Runway arrangement

ABSTRACT

A runway arrangement comprising: a first runway section ( 202 - 1 ) designated as a landing runway section; a second runway section ( 202 - 2 ) designated as a take-off runway section; and a sterile safety area ( 210 ); wherein the first and second runway sections are linked by the sterile safety area ( 210 ); the runway arrangement comprising a missed approach point for aircraft due to land on the first runway section, displaced from the start of the second runway section ( 202 - 2 ) by a distance greater than H/tan θ 1 ; where H is a safe turning height and θ 1  is an angle of ascent following a missed approach; wherein H is greater than 150 m and θ 1  is greater than 2°.

PRIORITY CLAIM TO RELATED APPLICATIONS

This application is a continuation and claims the benefit of priority ofU.S. application Ser. No. 15/302,775, filed 7 Oct. 2016, which is a U.S.national stage application filed under 35 U.S.C. § 371 fromInternational Application Serial No. PCT/GB2015/051089, which was filed9 Apr. 2015, and published as WO2015/155541 on 15 Oct. 2015, and whichclaims priority to United Kingdom Application No. GB 1406419.0, filed 9Apr. 2014, which applications and publication are incorporated byreference as if reproduced herein and made a part hereof in theirentirety, and the benefit of priority of each of which is claimedherein.

FIELD OF INVENTION

This invention relates to a runway arrangement and a method ofconstructing and operating the same. The invention also relates to alight or system of lights for a runway arrangement and a method ofoperating the same.

BACKGROUND

Airport capacity (the number of aircraft able to land and/or take offper hour) is often limited by the size, number and configuration of therunways. For safety reasons, there has to be a certain time and distanceseparation between aircraft landing and/or taking off on the samerunway. Often, multiple runways are used; designated either for landing,take-off or mixed mode (where runways are used for both take-offs andlandings in turn). This increases airport capacity, but multiple runwaysneed to be spaced sufficiently apart so as not to interfere with oneanother and to comply with regulatory and safety requirements. In urbanor other constrained environments, adequate space for an additionalrunway may not be readily available, and/or the noise footprint fromaircraft using a new runway may not be acceptable. Furthermore, theadded time and fuel incurred by taxiing aircraft to a runway furtherfrom the terminal may add to the operating cost and CO₂ emissions of theflight.

For safety of operation, and so as pilots are guided to the correctrunway section, according to an aspect of the present invention there isprovided a device for marking a runway section, the device comprising: alight source; and a light director.

Preferably, to guide landing aircraft, the light director is arranged soas to inhibit light directed towards an aircraft landing on said runwaysection emitted by the light source.

Preferably, the light director is adjustable between a first stateindicating a landing runway section and a second state indicating anon-landing runway section.

Preferably, the light director comprises a lens.

Preferably, the light director comprises means for selectively blockingthe light from the light source.

Preferably, the blocking means is angled with respect to the lightsource.

Preferably, the light director comprises an opaque covering.

Preferably, the light director comprises means for polarising light, andpreferably the polarising means comprises a polarising filter.

Preferably, the light directing means is movable with respect to thelight source.

Preferably, the light directing means is rotatable.

Preferably, the light source is adapted to be positioned on the edge ofa runway arrangement.

Preferably, the light source is adapted to be positioned on thecentreline of a runway arrangement.

According to another aspect of the present invention, there is provideda device for marking a runway section, having a plurality of devices formarking a runway section as described herein.

According to another aspect of the present invention, there is provideda device for marking a runway section; comprising a plurality of runwaylight sources adapted to be arranged along a runway section; a lightdirector for each runway light source; wherein the light director isarranged so as to inhibit light directed towards an aircraft landing onsaid runway section emitted by its respective light source; therebydesignating said runway section as a non-landing runway section. Such adevice allows for safe independent operation of a runway section

Preferably, the light director comprises an artificial vision system.Preferably, the artificial vision system comprises at least one of:head-up display, helmet-mounted display, and visual display.

Preferably, the light director is arranged so as to direct light fromthe light source towards aircraft on said runway section; therebydesignating said runway section as a take-off runway section.

Preferably, each light director is angled with respect to its respectivelight source in dependence on the light source's intended position alonga runway section.

Preferably, the light directors intended to be placed at a more proximalposition along said runway section are angled to a greater extent thanthose intended to be placed a more distal position along said runwaysection.

According to another aspect of the present invention there is provided arunway arrangement comprising a first runway section; a second runwaysection extending substantially in prolongation of the first runwaysection, said second runway section having a plurality of runway markingdevices each comprising a runway light source and a light director foreach runway light source; and an intermediate section between the firstand second runway sections; wherein each light director is arranged soas to inhibit light directed towards an aircraft landing on said firstrunway section towards said intermediate section emitted by itsrespective light source; thereby designating said second runway sectionas a non-landing runway section.

Preferably, so as to enable operation in either direction, the firstrunway section comprises a plurality of runway marking devices eachcomprising a runway light source and a light director for each runwaylight source; wherein each light director is arranged so as to inhibitlight directed towards an aircraft landing on said second runway sectiontowards said intermediate section emitted by its respective lightsource; thereby designating said first runway section as a non-landingrunway section.

Preferably, so as to enable ‘long landings’ to provide respite to localpopulation, the light directors are adapted to be adjusted so as todesignate the non-landing runway section as a landing runway section.

Preferably, so as to enable ‘long landings’ to provide respite to localpopulation, the non-landing runway section further comprises secondarylighting so as to designate the non-landing runway section as a landingrunway section.

Preferably, the light director is arranged so that light is directedtowards an aircraft on said non-landing runway section, therebydesignating said non-landing runway section as a take-off runwaysection.

Preferably, each runway light source comprises a light director.

Preferably, each runway marking device is a device as described herein.

According to another aspect of the present invention there is provided amethod of operating a runway arrangement having a runway lightingsystem, the method comprising: providing light sources along a first anda second section of a runway arrangement; and providing light directorsso as to inhibit light from the lights on said first runway sectionbeing directed towards an aircraft landing on said second runwaysection; thereby designating said second runway section as a non-landingrunway section. Such a method allows for safe independent operation ofthe two runway sections.

Preferably, the runway arrangement comprises the runway arrangement asdescribed herein.

According to another aspect of the present invention there is provided arunway arrangement comprising: a first runway section designated as alanding runway section; a second runway section designated as a take-offrunway section; and a sterile safety area; wherein the first and secondrunway sections are linked by the sterile safety area; the runwayarrangement comprising a missed approach point for aircraft due to landon the first runway section, displaced from the start of the secondrunway section by a distance greater than H/tan θ₁; where H is a safeturning height and θ₁ is an angle of ascent following a missed approach;wherein H is greater than 150 m and θ₁ is greater than 2°. Such anarrangement allows for safe independent operation of the two runwaysections whereby a landing aircraft performing a missed approach is lesslikely to interfere with another aircraft. The missed approach point maycomprise physical markings on the first runway section or may be definedby software.

Preferably, the missed approach point is between 1,500 m and 4,500 mfrom the start of the second runway section. Preferably, the missedapproach point is between 2,500 m and 3,500 m from the start of thesecond runway section. Preferably, the missed approach point isapproximately 3,000 m from the start of the second runway section.

Preferably, the missed approach point is a landing threshold marked onsaid first runway section.

Preferably, the landing threshold is between 100 m and 1,500 m from thestart of the second runway section. Preferably, the landing threshold isbetween 100 m and 1,000 m from the start of the second runway section.Preferably, the landing threshold is between 300 m and 800 m from thestart of the second runway section. Preferably, the landing threshold isbetween 500 m and 800 m from the start of the second runway section.

Preferably, the landing threshold is less than 850 m from the start ofthe second runway section.

Preferably, the landing threshold is substantially at the start of thesecond runway section.

Preferably, the second runway section is disposed at an angle to thefirst runway section.

According to another aspect of the present invention there is provided amethod of determining a safe approach on a runway arrangement, therunway arrangement comprising a first runway section designated as alanding runway section, a second runway section designated as a take-offrunway section, and a sterile safety area, wherein the first and secondrunway sections are linked by the sterile safety area, the methodcomprising: designating a missed approach point; and determining saidmissed approach point as being displaced from the start of the secondrunway section by a distance greater than H/tan θ₁; where H is a safeturning height and θ₁ is an angle of ascent following a missed approach.Such a method reduces the possibility of a landing aircraft performing amissed approach interfering with another aircraft departing from thetake-off runway section.

Preferably, H is greater than 150 m and θ₁ is greater than 2°.

According to another aspect of the invention, there is provided a runwayarrangement comprising a first runway section; a second runway section;and a sterile safety area; wherein the first and second runway sectionsare linked by the sterile safety area; and the second runway section isdisposed at an angle to the first runway section.

The geometry of the runway arrangement can provide a benefit to thelocal environment, for example, by preventing the need for demolition ofbuilt-up areas, including residential areas and providing relief to thelocal population. Furthermore, on-ground aircraft safety equipment, suchas Instrument Landing Systems (ILS), may be located such that they havea line-of-sight to aircraft approaching either the first or secondrunway sections.

Preferably, the second runway section is disposed at substantially0.1-10 degrees to the first runway section, preferably substantially0.25-10 degrees preferably substantially 1-5 degrees, more preferablysubstantially 2-3 degrees.

Preferably, second runway section is laterally offset from the firstrunway section, the lateral offset being in an opposite direction to thedirection the second runway section is angled, thereby preferablydecreasing interference between aircraft utilizing the first and secondrunway sections.

Preferably, in order to balance safety and minimise taxiing distance foraircraft to and from an airport terminal, the second runway section islaterally offset from the first runway section by between a quarter anddouble the width of the first runway section, preferably between 50 mand 100 m, more preferably between 60 m and 80 m.

The runway arrangement may further comprise a laterally offset runwaysection substantially parallel to, and preferably substantiallylongitudinally aligned with, said first runway section.

Preferably, in order to make use of the land within the envelope of therunway arrangement efficiently, the second runway section is angled fromthe safety area towards the laterally offset runway section.

Preferably, in order to ensure safety and prevent aircraft collisions ordisruption, the laterally offset runway section is laterally offset fromsaid first runway section so that the centerline of the laterally offsetrunway does not intersect with the second runway section, preferablywherein the runway arrangement satisfies the inequality D>L·sin(θ) orD+O>L·sin(θ); preferably wherein D is the lateral separation between thelongitudinally aligned runways, L is the length of the second runwaysection, θ is the angle that the second runway section is angled, and Ois the lateral offset of the first and second runway sections (asdefined further below).

Preferably, to improve airport capacity in a land-efficient manner,there is provided a third runway section substantially in prolongationof the first runway section, thereby preferably forming a ‘y-shaped’runway arrangement; and the first and third runway sections are linkedby a sterile safety area.

The sterile safety area between the first and third runway sections maybe linked to the sterile safety area between the first and second runwaysections.

Preferably, the third runway section is laterally offset from said firstrunway section, the lateral offset being in an opposite direction to theangle of the second runway section, thereby preferably affordingsimultaneous use of the first and third runway section.

Preferably, the third runway section comprises a sterile safety area atthe end of the runway section proximal to said first runway section.

Preferably, the sterile safety area at the end of the third runwaysection is substantially aligned with the sterile safety area betweenthe first and second runway sections.

Preferably, the second runway section is laterally offset from the firstrunway section, which consequently offsets environmental disruption, forexample, away from built-up areas.

Preferably, the runway arrangement comprises two further laterallyoffset runway sections substantially parallel to, and substantiallylongitudinally aligned with, said first and/or second runway sections,thereby preferably, for example, preventing the need for demolition ofmultiple built-up areas, including residential areas and providingrelief to a wider local population whilst also improving aircraftcapacity.

According to another aspect of the invention, there is provided a runwayarrangement comprising a first runway section and a second runwaysection; wherein the second runway section is laterally offset from thefirst runway section; and the second runway section longitudinallyoverlaps with the first runway section; a section not overlapping beingfor use as a take off or landing section.

The geometry of the runway arrangement can provide a benefit to thelocal environment, for example, by preventing the need for demolition ofbuilt-up areas, including residential areas and providing relief to thelocal population. Furthermore, on-ground aircraft safety equipment, suchas ILS, may be placed with a line-of sight to aircraft moving alongeither the first or second runway sections.

Typically, for safety, the landing section may be directed towards theoverlapping section and the take off section is directed away from theoverlapping section.

Preferably, the overlapping section is between 300 m and 900 m inlength, preferably substantially 400 m-600 m in length.

Preferably, the overlapping section is a sterile safety area; preferablythe sterile safety area is free from on-ground aircraft during normaluse of the runway arrangement, thereby preferably allowing theoverlapping section to be available for use by aircraft duringemergencies or in exceptional circumstances.

Preferably, in order to balance safety and minimise taxiing distance foraircraft to and from an airport terminal the second runway section islaterally offset from the first runway section by between a quarter anddouble the width of the first runway section, preferably between 50 mand 100 m, more preferably between 60 m and 80 m.

Preferably, there is provided a taxiway outside of the sterile safetyarea so as to allow access across the first runway section to theproximal end of the second runway section.

Preferably, in order to avoid flight path intersection, the secondrunway section is substantially parallel to the first runway section.

Preferably, the second runway section is disposed at an angle to thefirst runway section, thereby preferably shifting the effect that use ofthe second runway arrangement would have on a local environment andpopulation.

Preferably, the second runway section may be disposed at substantially0.1-10 degrees to the first runway section, preferably substantially0.25-10 degrees, preferably substantially 1-5 degrees, more preferablysubstantially 2-3 degrees.

Preferably, subject to the length of the second runway, the secondrunway section is angled relative to the first runway section so as toavoid flight paths or extensions to the runway arrangement fromcompromising the local environment or local populations.

According to a further aspect of the invention, there is a method ofproviding a runway arrangement comprising the steps: providing a firstrunway section; providing a second runway section; and providing asterile safety area; wherein the first and second runway sections arelinked by the sterile safety area; and the second runway section isdisposed at an angle to the first runway section.

Expansion of airport runway arrangements is thereby enabled, inparticular where expansion is otherwise restricted (due to, for example,geographic or social constraints).

Preferably, the second runway section is laterally offset from the firstrunway section, the lateral offset being in an opposite direction to theangle of the second runway section, in order to avoid potentialdisruption of local environs.

Preferably, in order to enable substantially double capacity, there isan additional step of providing two further laterally offset runwaysections substantially parallel to, and substantially aligned with, saidfirst and/or second runway sections.

Preferably, in order to increase capacity, a further laterally offsetrunway section substantially parallel to, and substantially alignedwith, said first runway section is provided, preferably wherein thesecond runway section is angled, preferably from the first runwaysection, towards the further laterally offset runway section.Preferably, the lateral offset distance between the first runway sectionand the laterally offset runway section, D, is 1,000 m-3,000 m, and morepreferably 1,400 m-1,600 m.

Preferably, for safety and in order to prevent intersection of flightpaths, the laterally offset runway section is laterally offset from saidfirst runway section so that the centerline of the laterally offsetrunway does not intersect with the second runway section, preferablywherein the runway arrangement satisfies the inequality D>L·sin(θ) orD+O>L·sin(θ), as defined below.

Preferably, in order to improve capacity whilst making efficient use ofland, a third runway section substantially in prolongation of the firstrunway section is provided, thereby preferably forming a ‘y-shaped’runway arrangement; and the first and third runway sections are linkedby a sterile safety area.

Preferably, the sterile safety area between the first and third runwaysections is linked to the sterile safety area between the first andsecond runway sections.

Preferably, the second runway section is laterally offset from the firstrunway section.

According to yet another aspect of the invention, there is a method ofproviding a runway arrangement comprising the steps of: providing afirst runway section; and providing a second runway section; wherein thesecond runway section is laterally offset from the first runway section;and the second runway section longitudinally overlaps with the firstrunway section; a section not overlapping being for use as a take off orlanding section.

Expansion of airport runway arrangements is thereby enabled, inparticular where expansion is otherwise restricted (due to, for example,geographic or social constraints).

Preferably, for efficiency, the landing section is designated for use ina direction towards the overlapping section and the take off section isdesignated for use in a direction away from the overlapping section.

Preferably, for safety, the overlapping section is a sterile safetyarea, preferably the sterile safety area is free from on-ground aircraftduring normal use of the runway arrangement.

Preferably, the second runway section is laterally offset from the firstrunway section by between a quarter and double the width of the firstrunway section, preferably between 50 m and 100 m, more preferablybetween 60 m and 80 m.

Preferably, a taxiway outside of the sterile safety area is designatedso as to allow access across the first runway section to the proximalend of the second runway section, preferably without the need to enterthe sterile safety area.

Preferably, to prevent intersection of flight paths, the second runwaysection is provided substantially parallel to the first runway section.

The second runway section may be provided at an angle to the firstrunway section.

According to yet a further aspect of the invention there is provided amethod of operating an airport runway arrangement for aircraft, themethod comprising the steps: directing an aircraft to move along a firstrunway section; directing an aircraft to move along a second runwaysection, wherein an aircraft is directed to move along the second runwayat an angle relative to and/or with a lateral offset from an aircraftdirected to move along the first runway section; and providing a sterilesafety area between the first and second runway sections. Aircraftflight paths may therefore be directed so as to avoid built-up areas.

Preferably, the step of directing an aircraft to move along the firstrunway section comprises directing an aircraft to land, preferablytowards the safety area.

Preferably, the step of directing an aircraft to move along the secondrunway section comprises directing an aircraft to take off, preferablyaway from the safety area.

Preferably, in order to provide relief to persons local to the airportrunway arrangement, the direction that an aircraft is directed to movealong the first and/or second runway section is reversed periodically,preferably daily.

Preferably, for safety, the step of directing an aircraft to taxi to thefirst or second runway section without, preferably under normaloperation, entering the safety area.

Preferably, an aircraft is directed to move along a third runway sectionthat is parallel to and/or laterally offset from the first runwaysection.

Preferably, for safety and in order to provide relief to localresidents, an aircraft is directed to move along a curved path whenapproaching and/or taking off from the first, second and/or third runwaysections.

Preferably, the first and second runway sections may be used as a singleextended runway (for example for long landings, long take offs or in anemergency) where the first and second runway sections extendsubstantially in prolongation of one another.

According to another aspect of the present invention, there is providedan airport comprising a runway arrangement as described above.Preferably the airport is London Heathrow airport, UK.

According to another aspect of the present invention, there is providedan airport system comprising an aircraft and at least one of: a runwayarrangement as herein described, and an air traffic control system asherein described.

According to yet another aspect of the present invention, there isprovided a method of controlling air traffic, being a method ofoperating an airport runway arrangement, preferably according to theaforementioned method of operation, wherein an aircraft is directed toand/or from the runway arrangement.

The invention extends to any novel aspects or features described and/orillustrated herein. Further features of the invention are characterisedby the other independent and dependent claims.

Any feature in one aspect of the invention may be applied to otheraspects of the invention, in any appropriate combination. In particular,method aspects may be applied to apparatus aspects, and vice versa.

Furthermore, features implemented in hardware may be implemented insoftware, and vice versa. Any reference to software and hardwarefeatures herein should be construed accordingly.

Any apparatus feature as described herein may also be provided as amethod feature, and vice versa. As used herein, means plus functionfeatures may be expressed alternatively in terms of their correspondingstructure, such as a suitably programmed processor and associatedmemory.

It should also be appreciated that particular combinations of thevarious features described and defined in any aspects of the inventioncan be implemented and/or supplied and/or used independently.

In this specification the word ‘or’ can be interpreted in the exclusiveor inclusive sense unless stated otherwise.

Furthermore, features implemented in hardware may generally beimplemented in software, and vice versa. Any reference to software andhardware features herein should be construed accordingly.

The invention extends to a runway arrangement, a method of providing arunway arrangement, a method of operating a runway arrangement, anairport and a method of controlling air traffic substantially as hereindescribed with reference to the accompanying drawings.

Preferred features of the invention are now described, purely by way ofexample, with reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

The invention extends to a runway arrangement, a method of providing arunway arrangement, a method of operating a runway arrangement, anairport and a method of controlling air traffic substantially as hereindescribed with reference to the accompanying drawings.

Preferred features of the invention are now described, purely by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is an example of an existing airport arrangement;

FIGS. 2(a) and 2(b) are examples of a runway arrangement where in-linerunways are utilised;

FIGS. 3(a), 3(b), 3(c) and 3(d) show the operation of an alternativerunway arrangement where offset runways are used;

FIG. 4 shows example landing approaches which may be used;

FIG. 5(a) shows a simplified illustration of the runway arrangements ofFIG. 2(a);

FIGS. 5(b), 5(c), 5(d) and 5(e) show modifications of the runwayarrangement shown in FIG. 5(a);

FIG. 6 shows an inline, angled runway arrangement;

FIGS. 7(a) and 7(b) show the runway arrangement of FIG. 6 with a furtherrunway section;

FIGS. 8(a), 8(b), 8(c) and 8(d) show runway arrangements correspondingto a combination of FIGS. 5(a), 5(b), 5(c), 5(d), 5(e) and 6;

FIGS. 9(a), 9(b) and 9(c) show runway arrangements corresponding to acombination of FIGS. 7(a) and 7(b), and 8(a), 8(b), 8(c) and 8(d);

FIG. 10 shows two sets of the inline, angled runway arrangements asshown in FIG. 6.

FIG. 11(a) shows a schematic plan view of a ‘go around’ performed by alanding aircraft;

FIG. 11(b) shows a corresponding schematic side view of a ‘go around’performed by a landing aircraft;

FIG. 12 is a graph indicating an example relationship between thedistance between the last point of touch down and the start of thetake-off runway (D) and the angle of ascent of an aircraft performing ago-around (θ₁);

FIG. 13 shows a perspective view of the runway arrangement of FIG. 2(a)including a runway lighting system;

FIG. 14 shows a perspective view of the runway arrangement of FIG. 2(a)including an alternative runway lighting system including secondaryrunway lights;

FIG. 15 shows a perspective view of the sightline of pilots landing andtaking off from the runway arrangement of FIG. 14;

FIG. 16 shows a side-on schematic view of the sightline of pilotslanding and taking off from the runway arrangement;

FIGS. 17(a) and 17(b) show example selectively blocked runway lights;and

FIGS. 18(a) and 18(b) show example runway lights with an opaquecovering.

SPECIFIC DESCRIPTION

The term ‘runway’ used in this description preferably refers to an areadesignated and certified by the regulatory and safety authorities foruse by an aircraft for taking-off and/or landing. Typically, this is asuitably hard surfaced area which is demarcated (i.e. distinct totaxiways etc.) as a runway. Throughout, the term ‘sterile’ is used torefer to the designation of an area that is preferably to be free fromon-ground aircraft, including any aircraft that are taxiing or beingmanoeuvred, under normal operation (i.e. except in emergencies andadverse conditions).

Furthermore, the term “safety area” or, interchangeably, “sterile safetyarea” (which may include “Intermediate Safety Areas” (“ISAs”) or“Intermediate Safety Sections” (“ISSs”)) preferably connotes an area orsection of runway that is sterile for the purposes of safety. An areadesignated as a safety area is not used during normal operations, butpreferably is only used in the event of an undershoot, overshoot,excursion from the runway, long landing or long take offs, andpreferably is not used in the case of a manoeuvre across the runway.Preferably, safety areas are variable or movable. Preferably, safetyareas are removable or variable, for example in the event that theentire runway is used for an aircraft manoeuvre (such as take-off orlanding). Each section of runway is suitably marked so that aircraftpilots can see where the section of runway designated respectively forarriving and departing aircraft starts and finishes. A person skilled inthe art would realise that a wide variety of runway markings andlighting that are currently known in the art would be suitable. The term“intermediate” with reference to safety areas herein preferablysignifies that a safety area is in between runway sections in a mannerthat links the runway sections by providing a surface in which aircraftmay manoeuvre between runway sections that are linked by theintermediate safety area via the intermediate safety area, albeit onlyin exceptional circumstances or adverse conditions.

In the description below the term ‘longitudinal length’ or ‘length’preferably refers to the length of the runway along which an aircrafttypically moves when landing or taking-off. The term ‘lateral width’ or‘width’ preferably refers to the width of the runway, or group ofrunways (depending on context), measured perpendicularly to thelongitudinal length.

Existing commercial airports for passenger carrying aircraft often havetwo or more runways to increase the capacity over a single runway. Theconfiguration of these runways depends on the layout of the airportterminal(s), the space (land) available, the surrounding geography andthe prevailing weather conditions (amongst other factors).

FIG. 1 shows an example of an existing airport arrangement 100 using tworunways 102, 104. This arrangement is common where the two runways 102,104 are sufficiently far apart so as not to interfere with one another'soperations during normal use, and each runway is close to the terminal106, or alternatively an aircraft-parking stand. Each runway is oftendesignated as a landing or take-off runway, or as mixed mode whereaircraft use the same runway for both landing and taking off in turn,with the aircraft moving in the same direction. Such designations maynot be permanent, and, for example, may be dependent on time of day orwind conditions.

Adding a third runway (shown by dotted runways 108) to such an existingarrangement would inevitably either interfere with operations, as shownby runway 108-1, or require a long taxi from the terminal 106 or theaircraft-parking stand, as shown by runway 108-2. This arrangement mayalso require aircraft to cross runway 102 when taxiing between runway108-2 and the terminal or aircraft-parking stand. Such arrangements ofadditional runways may also make ‘go-arounds’ (where an aircraft abortsapproach or landing and loops round for another attempt) more dangerousas the aircraft may have to cross the flight path of other aircraftapproaching or departing from the other runways.

An alternative runway arrangement for commercial, passenger carryingaircraft operating under civil regulations is shown in FIG. 2(a) where asingle runway is split into two sections 202-1, 202-2 separated by anintermediate area 210-3. In the example shown, the first runway section202-1 is used as a landing runway and the second runway section 202-2 isused as a take-off runway. The total runway length of this arrangementis longer than those shown in FIG. 1 to allow aircraft to simultaneouslyland and take-off from each section of the runway. Safety areas 210-1and 210-2 are provided as required by regulatory and safety authoritiesat each end of the runways (where they may be called Runway End SafetyAreas (RESAs)) to reduce the risk of damage to aircraft in the event ofan undershoot, overshoot, or excursion from the runway. A similarintermediate safety area 210-3 to fulfil the same purpose (that is,preferably, to reduce the risk of damage to aircraft in the event of anundershoot, overshoot or excursion from the runway, as appropriate, ofaircraft) is provided at the boundary between the two sections ofrunway.

A “go-around” is shown in FIG. 2 (a) indicating how landing aircraftturn away from the runway in the event of an aborted approach orlanding. This occurs at the start of the landing section 202-1 andtherefore avoids conflict with departing aircraft.

FIG. 2(a) shows equal length runway sections each side of theintermediate safety area. However, the position of the intermediatesafety area is not fixed, allowing the length of the runway sectionseach side to be increased or decreased in length according to operatingrequirements. Preferably, the safety areas 210 are adjustable withrespect to their dimensions and/or positions depending on the winddirection and spatial requirements of landing and departing aircraft.

This runway arrangement can also be used in the opposite direction ofoperation, i.e. the runway section 202-1 being used as a take-off runwayand section 202-2 being used as a landing section. Preferably, in use,the directions of operation of the runway sections 202 are switchable.

A runway arrangement for commercial, passenger carrying aircraftoperating under civil regulations, identified generally by the referencenumeral 200, where a pair of runways is provided, is shown in FIG. 2(b).In the example shown, the first runway sections 202-1 and 204-1 are usedas landing runways and the second runway sections 202-2 and 204-2 areused as take-off runways. The total length of each runway of thisarrangement is longer than those shown in FIG. 1 to allow aircraftsimultaneously to land and take-off from each section of the runway.

Safety areas 210-1, 210-2, 210-3 and 210-4 are provided as required byregulatory and safety authorities at the each end of runway (where theymay be called Runway End Safety Areas (RESAs)) to reduce the risk ofdamage to aircraft in the event of an undershoot, overshoot, orexcursion from the runway. A similar intermediate safety area 210-5 and210-6 to fulfill a similar purpose and to allow fully independentoperation of the two runway sections 202-1, 202-2 is provided at theboundary between the two sections of runway. Each section of runway issuitably marked so that aircraft pilots can see where the section ofrunway designated respectively for arriving and departing aircraftstarts and finishes. A person skilled in the art would realise that awide variety of runway markings and lighting that are currently known inthe art would be suitable. Preferably, the safety areas 210 aremovable/variable by adjusting the associated markings (e.g. lighting) onthe runway. Preferably, the safety areas 210 are sterile under normaloperation, in that the areas are free from on-ground aircraft, includingany aircraft that are taxiing or being maneuvered. Preferably the safetyareas 210 are free from aircraft that are taxiing or being maneuveredacross the runway.

In one example, one and the same intermediate safety area is used forlanding and take-off. If, in an emergency, such as an overshoot, alonger portion of runway is needed, then the intermediate safety area(typically in the form of a set of runway markings, for example lights)is varied so as to designate a longer portion of runway. In one example(with the figures given being approximate to the nearest 5 or 10%), arunway that is 6400 m long in total has a 2800 m long first runwayportion, an intermediate safety area 400 m in length and a second runwayportion that is 3200 m in length. Alternatively, there is a 2600 m longfirst runway portion, an intermediate safety area 600 m in length and asecond runway portion that is 3200 m in length. In a further alternativeexample, there is a 2800 m long first runway portion, an intermediatesafety area 600 m in length and a second runway portion that is 3000 min length. In each of the above examples, at least two sets of markingsare used in order to accommodate adjustments to the length of the runwayand/or the direction of operation of the runway arrangement. Thetake-off runway length is available to be made longer by the length ofthe intermediate safety area (e.g. an additional length of 600 m or 400m as per the above examples) or a portion of the length of theintermediate safety area, since the intermediate safety area ispreferably redundant for take-off, but is preferably required forlanding. The designation of the intermediate safety area is varied fordifferent directions of operation of the runway arrangement. Preferably,there are at least two intermediate safety areas or four intermediatesafety areas in two, preferably contiguous, pairs (for example, one pairfor Westward operations and another pair for Eastward operations).Preferably, the intermediate safety area is available to be partitionedinto a plurality of component portions so as to allow greatergranularity in the adjustment of the intermediate safety area and thelength and/or position of runway sections.

FIG. 2(b) shows equal length runway sections each side of theintermediate safety area 210-5 and 210-6. However, the position of theintermediate safety area is not fixed, allowing the length of the runwaysections each side to be increased or decreased in length according tooperating requirements.

A “go-around” is shown for both landing runways in FIG. 2(b) indicatinghow landing aircraft turn away from the runway in the event of anaborted approach or landing. This occurs at the start of the landingsections 202-1 and 204-1 and therefore avoids conflict with departingaircraft.

This runway arrangement can also be used in the opposite direction ofoperation, i.e. the runway sections 202-1 and 204-1 being used astake-off runways and sections 202-2 and 204-2 being used as landingrunways. Reversing the direction of operation of the runways in this waywould be particularly advantageous where the wind direction changes ordifferent directions of approach are preferred at different times ofday, for example to limit aircraft noise on areas around the airport.Flexibility in the adjustment of the position and/or size of the safetyareas 210 helps facilitate dual-direction operation.

Dashed lines show typical aircraft movements on the ground to and fromthe taxiways 212. A person skilled in the art will appreciate thataircraft ground movements are in reality more complicated than shown butground movement of arriving and departing aircraft is possible withoutconflict.

Table 1 below shows dimensions of an example runway arrangement in FIGS.2(a) and 2(b):

TABLE 1 Example dimensions of elements of a runway arrangement Referencenumeral Description Length 202-1, 202-2, 204-1, 204-2 Runway sections2200-3200 m 210-1, 210-2, 210-3, 210-4 Runway end safety ≥300 m areas210-5, 210, 6 Intermediate safety 300-600 m areas d Runway separation≥1035 m

The lengths provided in Table 1 are purely by way of example and dependon various factors such as the type of aircraft that use the runway andthe space available. For example, the runway sections may be between1000 m and 8000 m long, preferably between 2000 m and 4000 m in length.Similarly, the dimensions of the RESAs and the intermediate safety areasmay be longer or shorter as defined by local regulatory requirements; inone preferred example they are between 240 m and 600 m in length, butpreferably up to 1500 m in length. The intermediate safety area ispreferably at least 175 m, 180 m, 200 m, 240 m, 250 m or 300 m inlength. Furthermore, the runway separation (d) is often defined by localregulations and may be longer or shorter.

By extending the length of existing runways and taxiways at an airport,the arrangements shown in FIGS. 2(a) and 2(b) can substantially increasecapacity without the need to construct entirely new runways which mightexpose more areas around the airport to aircraft noise. Improving theefficiency of an airport by increasing capacity reduces the need forarriving aircraft to be held in ‘stacks’ circling whilst waiting for alanding slot, and thus reduces overall CO₂ emissions per flight.Furthermore, the runway arrangement shown increases efficiency andcapacity, reduces taxiing distances compared to multiple runway layouts,and reduces hold times for aircraft awaiting a take-off slot, which alsoreduces the CO₂ emissions per flight.

The arrangement shown in FIGS. 2(a) and (b) may be somewhat limiting incertain examples if regulatory and safety authorities require departingaircraft to wait for a landing aircraft to slow to a safe speed beforethe departing aircraft is allowed to enter the take-off section of therunway.

FIG. 3 show an alternative embodiment identified generally by thereference numeral 300, where the landing sections 302-1, 304-1 areoffset laterally from the respective take off sections 302-2, 304-2.This reduces the risk of any perceived potential conflict betweenarriving and departing aircraft. The total width of each runway 302, 304is greater than that of FIGS. 2(a) and (b) (say 70 m to 170 m preferably85 m to 95 m, as opposed to 40 m to 50 m, but in any event as requiredby the regulatory and safety authorities), whilst runways and taxiwaylengths are extended in the same way as those shown in FIG. 2.

This arrangement would be particularly advantageous where an existingrunway is wider than is required by the regulatory and safetyauthorities and can be divided longitudinally to provide two contiguous,parallel runways. Alternatively, the existing runway can be widened, toone or both sides, to provide the required width.

FIGS. 3(a), (b), (c) and (d) illustrate the ways in which this runwayarrangement can be used. FIGS. 3(a) and (b) illustrate two arrangementswhen Southerly operations are used and FIGS. 3(c) and (d) show thecorresponding runway arrangements when Northerly operations are used. Inone example, a switch in runway operation modality from that shown inFIGS. 3(a) to 3(c) would represent a change from Southerly to Northerlyoperations; the designation of the safety areas is adjusted accordingly.

The positions and/or preferably the length of the intermediate safetyareas vary as shown by the different arrangements, allowing the lengthof the runway sections each side to be increased or decreased in lengthas shown and according to operating requirements. Preferably, the lengthof the intermediate safety area is dynamically varied in dependence ofvarious factors, including aircraft propulsion blast effects, aircraftperformance effects and/or obstacle limitation surfaces (for example, soas to allow a departing aircraft adequate clearance past potentialobstacles, such as the tail fin of a ground aircraft). Examples of wheredifferent length runways and/or preferably intermediate safety areaswould be advantageous is where light/medium aircraft land and take offfrom shorter sections and large/heavy aircraft land and take off fromthe longer sections. This arrangement also avoids the problem of smalleraircraft being affected by the vortices produced by large aircraft whichhave landed/taken off immediately beforehand. The lengths of thesesections could be tailored to the exact type of aircraft using therunway arrangement and would not necessarily be permanent. Table 2 showsexample dimensions for such a scenario:

TABLE 2 Example dimensions of elements of a runway arrangement Referencenumeral Runway type Length 302-1 Landing - large/heavy 2500-4000 m 302-2Take-off - light/medium 1000-2500 m 304-1 Landing - light/medium1000-2500 m 304-2 Take-off - large/heavy 2500-4000 m

The lengths provided in Table 2 are purely by way of example and dependon various factors such as the type of aircraft that use the runway andthe space available. For example, the overall length of each runway 302,304 may be between 3000 m and 8000 m, preferably between 4000 m and 6000m, more preferably approximately 5400 m (excluding intermediate safetyareas). In a preferred example the longer runways 302-1,304-2 aresubstantially 3200 m long and the shorter runways 302-2, 304-1 areapproximately 2200 m long. Preferably, the total length of the runwayarrangement is at least 5000 m, 6000 m, 6400 m, 6600 m, 6800 m or 7000 min length. This may extend the runway arrangement beyond the existingbounds of the airport, possibly into a less densely populated area,which might bring noise advantages as described later in relation toFIG. 7.

Safety areas 310-1, 310-2, 310-3 and 310-4 are provided as required byregulatory and safety authorities at each end of the runway (where theymay be called Runway End Safety Areas (RESAs)) to reduce the risk ofdamage to aircraft in the event of an undershoot, overshoot, orexcursion from the runway. A similar intermediate safety area 310-5 and310-6 to fulfil the same purpose is provided at the boundary between thetwo sections of each runway. Each section of runway is suitably markedso that aircraft pilots can see where the section of runway designatedrespectively for arriving and departing aircraft starts and finishes. Aperson skilled in the art would realise that a wide variety of runwaymarkings and lighting that are currently known in the art would besuitable. Preferably, the safety areas 310 are movable by adjusting theassociated markings on the runway.

Preferably, the safety areas 210 are sterile under normal operation, inthat the areas are free from on-ground aircraft, including any aircraftthat are taxiing or maneuvering, preferably the safety areas 210 beingfree from aircraft that are taxiing or maneuvering across the runway.

A “go-around” is shown for both landing runways in FIGS. 3(a), (b), (c)and (d) indicating how landing aircraft turn away from the runway in theevent of an aborted approach or landing. Such a manoeuvre may also becalled a ‘missed approach’. This occurs at the start of the landingsections 302-1 and 304-1 (FIGS. 3(a) and (b)) and landing sections 302-4and 304-4 (FIGS. 3(c) and (d)) and therefore avoids conflict withdeparting aircraft. The outer pair of runways (302-1 and 304-1 in FIGS.3(a) and (b) and 302-4 and 304-4 in FIGS. 3(c) and (d)) are designatedas landing runways to allow aircraft to turn away from the runwaywithout conflicting with departing aircraft on the inner pair ofrunways.

In FIGS. 2 and 3 designating areas as safety areas 210 and 310 maycomprise physical changes such adding lighting, runway markings and/orsoftware-implemented changes such as alerting pilots and air-trafficcontrollers to the runway length available via a user interface. Thesedesignations may be altered by a user and/or computer system alteringthe active lighting and/or markings on the runway and makingcorresponding changes to the user interface display for the pilots andair traffic controllers. Such a system would allow flexibility in thelocation of intermediate safety areas. Also, in the event of an aircraftneeding a much longer runway than usually required, the full length ofeach runway could be used since the intermediate safety areas, as wellas being flexible in location, can also be used as part of the runway ifrequired (in such a scenario, no intermediate safety area is provided).Such an arrangement would however remove the increased capacity gainscompared to having two independent, in-line runway sections.

Instrument Landing Systems (ILS), used to aid landing, are typicallyarranged such that the aerials of the ILS are placed at the distal endof a runway. With reference to FIGS. 2(a) and 2(b), ILS signaldegradation is expected due to the distance between a landing aircraftand the ILS aerial, in addition to potential obstruction from departingaircraft. The offset of runway sections 302-1 and 304-1 from runwaysections 302-2 and 304-2 respectively, as shown in FIGS. 3(a)-(d),allows the ILS aerials to be preferably placed nearer to landingaircraft, immediately beyond the landing runway section (e.g. runwaysections 302-1 and 304-1 in FIG. 3(a)). In this manner, the ILS aerialhas free line-of-sight to landing aircraft, is more proximate to landingaircraft and is safely offset from departing aircraft. To improvesafety, preferably fixed, but frangible ILS aerial structures are usedso as to prevent damage to aircraft, for example in an aircraft landingincident. Additionally, the ILS aerial is low-lying so as to avoidcontact with aircraft wings.

FIG. 4(a) shows an alternative method of using the runway arrangementsdescribed above. There are often restrictions on airport operationsearly in the morning or late at night due to the noise involved and theconsequent disturbance to the surrounding population.

During times where aircraft are only landing, for example, earlymornings, the whole length of one or both runways is available forincoming aircraft. Thus, aircraft can land at the distal end of anyrunway, thus effectively moving the noise further down the runway. Thiscould be by several thousand metres for a long runway. Thus, the runwayis effectively this extra distance further away from the localpopulation, reducing the intensity of the noise for people along theflight path. FIG. 7(a) shows points 700 where aircraft would usuallyland (see FIGS. 2 to 4 and above) relative to points 702 where aircraftcan land if there are no aircraft taking off.

During times when aircraft are only taking off, for example, lateevenings, the whole length of one or both runways is available fordeparting aircraft. Thus, aircraft can similarly start their take offfrom further down the runway.

FIG. 4(b) shows the effect of this different landing method on a nearbypopulation 704 a distance x away. The normal flight path 706 passes overa point directly above the population 704 at a distance d. When usingthe ‘long landing’, where the landing point is offset by a distance Δx,the new flight path 708 is at a distance d+Δd above this same point.This distance is given by the following relationship:Δd=Δx·tan θ

Extending the landing point by say 2 km with a descent gradient of 3°therefore means a higher flight path by around 105 m. This has asignificant impact on the noise levels at the ground. The further thelanding point is extended, the higher the aircraft will be at a givenpoint away from the start of the runway. This distance is limitedhowever by the available runway length; 2 km is merely an example andthe distance may be greater or smaller than this depending on the runwaybeing used.

A similar method can be used when taking off so that aircraft haveclimbed to a greater distance when they pass over a nearby population.In such operation, aircraft begin the take-off at an end of a runway, asopposed to nearer the middle as shown in FIGS. 2 to 4. Such operationwould occur independently to aircraft landing.

Designation of landing thresholds and/or safety areas may comprisephysical changes such as adding or removing lighting, additional runwaymarkings (such as threshold markings) and/or alerting pilots andair-traffic controllers to the position of the safety areas, runwaylength and/or position, possibly using software-implemented changes suchas alerting pilots and air-traffic controllers to the runway lengthavailable via a user interface. These designations may be altered by auser and/or computer system altering the active lighting and/or markingson the runway and making corresponding changes to the user interfacedisplay for the pilots and air-traffic controllers. Such a system allowsflexibility in the length and/or position of the runway, direction ofoperation and permits ‘long landing’ to be facilitated. The full lengthof each runway could be used since the intermediate safety areas, aswell as being flexible in location, can also be used as part of therunway if required.

FIG. 5(a) shows a simplified version of the runway arrangement shown inFIG. 2(a) with detail such as the RESAs omitted for clarity. A firstrunway section 502-1 and a second runway section 502-2 are linked by asterile safety area 510, intermediate with the first and second runwaysections (hence also referred to as an Intermediate Safety Area (ISA)).The term ‘linked’, with reference to the sterile safety areas and FIGS.5-10, is herein used preferably to refer to an area that extendscontinuously between runway sections (in effect connecting the runwaysections), such as the first 502-1 and second 502-2, wherein aircraftare able to, if need be, manoeuvre between the first and second runwaysections via the safety area. In one example, the sterile safety area510 section is between 300 m and 900 m in length, preferably 400 m-600 min length. The sterile safety area 510 being sterile preferably meansthat aircraft do not typically use this area for landings, take-offs ortaxiing during normal operation. The sterile safety area 510 istherefore free from, preferably on-ground, aircraft movement, typicallybeing reserved for emergency situations.

In overview, FIGS. 5(b)-5(e) depict runway arrangements that aremodified over that shown in FIG. 5(a), with (in FIGS. 5(b)-5(e)) thefirst runway section 502-1 laterally offset from the second 502-2.

Specifically, FIG. 5(b) shows a modification of the arrangement shown inFIG. 5(a) whereby the ends of the first and second runway sections502-1, 502-2 are laterally offset from one another and longitudinallyoverlap. The first and second runway sections 502-1, 502-2 are laterallyoffset by a distance O (measured centreline to centreline between theends of the runway sections).

The lateral offset may be beneficial for environmental purposes (forexample, by preventing the need for demolition of built-up areas,including residential areas) and providing relief to the localpopulation. For this to be the case, the amount of runway that is notoverlapping must be sufficient for an aircraft to land and/or take-off,the overlapping portion being used in emergency situations or for phasedlandings/take offs (for example for particularly heavy aircraft orduring adverse weather conditions). Safety advantages may also arise byshifting flight paths away from populated areas due to the offset in therunway sections.

FIG. 5(c) shows the first runway section 502-1 located closer to theterminal 106 than the second runway section 502-2 is located to theterminal. FIG. 5(d) is related to FIG. 5(c) but shows the first runwaysection 502-1 located farther from the terminal 106 than the secondrunway section 502-2 and the first runway section 502-1 extendingEastwards, while the second runway section 502-2 is arranged Westwards.The runway arrangement shown in FIG. 5(c) is used where, for example,the first runway section 502-1 is a pre-existing runway and expansion ofthe runway arrangement to the West is not feasible (for example, due togeographic or socio-environmental constraints, such as the presence of areservoir, motorway or built-up area, which may, for example, correspondto Wraysbury, The Queen Mother or King George VI reservoirs; and the M25motorway, in the case of London Heathrow airport, UK). Conversely, thearrangement shown in FIG. 5(d) is used when expansion of a runwayarrangement to the West is feasible (and therefore expansion to the Eastis not feasible, for example due to the presence of a built-up area,such as Cranford, London, UK in the case of London Heathrow airport) byproviding the second runway section 502-2 (and also in which the secondrunway section 502-2 is provided more proximately to the terminal 106than there first runway section 502-1). FIG. 5(d) illustrates oneexample where a single sterile safety area 510-1 extends, from a regioncoincident with the longitudinally overlapping section (as shown in FIG.5(b)), between the first 502-1 and second 502-2 runway sections, therebylinking the two runway sections.

In other examples, two distinct sterile safety areas 510-1 and 510-2 aredesignated, as shown in FIG. 5(c). Each runway section 502 comprises asterile safety area 510, which in one example is coincident with theoverlapping section (as shown in FIG. 5(b)), forming a single sterilesafety area. In one example, the longitudinal overlapping section isbetween 300 m and 900 m in length, preferably between 400 m and 700 m inlength, and more preferably between 400 m and 600 m in length.

In normal operation, taxiways T are used (indicated by solid lines)whereby aircraft utilise only the length of the runways not designatedas a safety area. In use, aircraft move in the same direction—taking offaway from the sterile safety area 510 (for example, with reference toFIG. 5(b), using section 502-1 in Westerly operations and 502-2 inEasterly operations) and land towards the sterile safety area (forexample, with reference to FIG. 5(b), using section 502-2 in Westerlyoperations and 502-1 in Easterly operations). Long landings/take offs,as described above with reference to FIG. 4, can also be performed. Moredetail relating to the modes of operation is provided below in Table 3.

In exceptional circumstances (for example, where a plane is particularlyheavy or due to adverse weather conditions), the entire length of arunway section may be used; however, as discussed above, independentoperation may not be possible under such circumstances. The taxiways T′used in such circumstances are indicated by dashed lines. For example,in Westerly operations (aircraft moving towards the left of FIG. 5(b))an aircraft requiring additional runway length to take off may cross thelower runway section 502-2 outside of the sterile safety area 510-2 andutilise the sterile safety area of the upper runway section 502-1 totake off. Similarly, if a greater distance is required to land, anaircraft may utilise the sterile safety area 510-2. An exact analogousarrangement is present when Easterly (towards the right of FIG. 5(b))operations are being used.

The sterile safety areas 510 are not used for taxiing purposes; aircrafttaxi either side of it and only pass through (and completely through)when executing an extended take-off or landing. If the runways are beingused in the ‘exceptional’ mode as described above, departures andlandings may need to be phased so as to allow aircraft to cross. Forexample, and with reference to FIG. 5(c), the second runway section502-2 is crossed (but not its associated safety area 510-2) to accessthe proximal end of the first runway section 502-1. This operationalrestriction makes it less likely that an aircraft is present in thesterile safety area 510 when there is no such phasing (e.g. if a pilotbelieves he has permission to use an extended runway when the airtraffic controllers have not arranged for phased departures/landings).

In another variant (see FIG. 5(e)), the distance (measured fromcentreline to centreline between the ends of the runway sections) therunway sections 502 may be offset may vary from less than a runwaywidth, for example a quarter of the width of a runway or 10 metres (i.e.so the runway sections 502 laterally overlap, as shown in FIG. 5(e)), upto a distance of approximately double the width of the runway or 100 m.In one example, the lateral separation is a distance of around the widthof the first runway section 502-1 so that the runway sections arecontiguous. In these two examples, the sterile safety areas 510 of eachrunway section may be combined into a single sterile safety area 510, asillustrated in FIGS. 5(d) and (e).

In another example, the minimum lateral separation is 60 m to 80 m dueto the regulations for runway widths at major airports (or ‘code F’runways, as present at Heathrow London airport), or, for example, theclearance surfaces in place at the airport. The greater the lateralseparation, the safer the arrangement is for use by aircraft. However,increasing the lateral separation requires a larger total space anddistance over which aircraft are required to taxi; therefore, a lateralseparation greater than, for example, 60 m to 100 m is inefficient.

ILS aerials 512 may be installed at the distal end of each runwaysections 502; such placement allows the aerials to be placedsufficiently close to landing aircraft, have free line-of-sight tolanding aircraft and be a safe distance from departing aircraft. Toimprove safety, preferably fixed, but frangible Instrument LandingSystem (ILS) aerial structures or other operational equipment are usedso as to prevent damage to aircraft, for example in an aircraft landingincident. Additionally, the ILS aerials may be low-lying, so as to avoidcontact with aircraft wings in case of runway excursions.

Landing guidance systems, such as Microwave Landing Systems (MLS) orother electronic systems, are preferably available to be installedalongside the aforementioned runway arrangements (in addition to orinstead of ILS) in order to aid landing. Advantageously, signalinterference and restrictions on placement of components of MLSinstrumentation, as observed in ILS, are overcome.

FIGS. 5(b)-(e) therefore depict examples of laterally offset runwaysections, which are particularly advantageous over laterally alignedrunway arrangements, for example as shown in FIGS. 2(a) and 5(a), asbuilt-up areas that lie below a flight path from a runway arrangementthat has laterally aligned runway sections may be avoided.

FIG. 6 shows a further runway arrangement comprising first and secondrunway sections 602-1, 602-2, wherein the second runway section 602-2extends from the first runway section 602-1 at an angle, via a safetyarea 610 that links the two runway sections. The two runway sections arethus effectively uninterrupted save for the (intermediate) safety area610. The second runway section 602-2 is disposed at an angle θ to thefirst runway section 602-1. The angle θ is greater than zero degrees. Inone example, where the runway sections apply for example to LondonHeathrow Airport, UK, the angle θ is between 0.25° and 10°, typicallybetween 0.5° and 8°, preferably between 1° and 5° and more preferablybetween 2° and 3°. Of course, the angle at which the second runway 602-2is disposed depends on, amongst other factors, the length of the secondrunway section and the location of any obstacles (e.g. built-up areas,such as Cranford, London, UK) which are to be avoided. Such anarrangement allows for greater safety as it would be very unlikely foran aircraft to encroach significantly onto the other runway whenovershooting the runway end. Furthermore, a slightly canted arrangementreduces the overall length required for the runway arrangement, reducingthe additional length of the additional runway section 602-2 by a factorof cos θ.

The example shown in FIG. 6 therefore provides at least the sameadvantage as the arrangements illustrated in FIGS. 5(b)-(e) in thatbuilt-up areas that may otherwise lie below a flight path (based on anarrangement that does not have an angled runway section) may be avoided.Furthermore, positioning the second runway section 602-2 at an angle tothe first section 602-1 has a similar advantage to laterally offsettingthe sections as described above with reference to FIGS. 5(b)-(e),insofar as ILS aerials 512 can be positioned with a line-of-sight to thelanding aircraft.

In overview, FIGS. 7-10 illustrate further examples of runwayarrangements that include at least three runway sections and thereforeprovide the potential for greater aircraft throughput than the examplesshown in FIGS. 5 and 6. In all of these examples the example lengths ofthe various sections provided in Tables 1 and 2 above, or elsewhere withreference to FIGS. 2-4, may apply.

In more detail, FIGS. 7(a) and (b) show runway arrangements thatcomprise three runway sections, wherein one of the runway sections issubstantially parallel and longitudinally aligned and preferablylaterally offset from another of the runway sections by a distance D.

As illustrated in FIG. 7(a), if there is a further runway 652 present,the angled runway 602-2 is preferably angled from the first runwaysection 602-1 towards this further runway 652 so that the additionalrunway section 602-2 remains within the existing envelope of theairport. This would mean that a population which would have beendisplaced by the runway extension may not necessarily be so. Withreference to FIGS. 7-10, the further runway 652 corresponds to theSouthern runway of London Heathrow airport and the first runway sectionmay correspond to the Northern runway of London Heathrow airport, orvice versa.

The length (L) and angle (θ) of the additional runway section 602-2 isdetermined by a number of factors:

-   -   1. The separation (D) between the two parallel runway sections        602-1, 652.    -   In order for both runways to be used simultaneously, there must        be no conflict of approach/departure paths on the two runway        sections. At the least, the centreline (C) of the further runway        652 does not intersect with the additional runway section 602-2.        For this to be the case, the following inequality must hold:        D>L·sin(θ)    -   As D is likely to be fixed by the pre-existing runway        arrangement, this inequality puts upper limits on L and θ. In        order to maximise L and θ whilst maintaining safe        approaches/departures, curved approaches/departures may be used        (as illustrated—in an exaggerated fashion).    -   The parameters of the curved approach/departure vary in        dependence on the speed, size, and distance from the centreline        of the runway, of the aircraft. The angle of bank for a curved        approach/departure changes with wind speed (as an aircraft's air        speed changes, but groundspeed does not). Typically, the        diameter of a curved approach/departure is about 1,000 m-2,000        m.    -   2. The proximity to terminals 106 and other infrastructure.    -   If pre-existing infrastructure (such as terminals 106) is to be        retained, this places restraints on the angle (and starting        point) of the additional runway section 602-2. In particular,        the height of pre-existing infrastructure may be determinative        of the angle θ and/or the starting point of the additional        runway section 602-2; this is typically governed by regulation;        for example, an approach/departure slope of approximately 1 in 7        starting 60 m out from the runway may be adopted.    -   These requirements may be circumvented to an extent by laterally        offsetting the second (angled) runway section 602-2 to the first        runway section 602-1. FIG. 7(b) shows an arrangement where the        centrelines of the second runway section 602-2 are laterally        offset from the centreline of the first runway section 602-1 by        a distance O (measured centreline to centreline between the ends        of the runway sections). This changes the equality above to the        following:        D+O>L·sin(θ)    -   When considering the case where D is fixed, the greater O is,        the larger the angle or length of the second runway section        602-2 may be without interfering with the first and the further        runway sections 602-1, 652. As O increases, the chances of an        aircraft overshooting onto the first runway section 602-1        decreases. However, the greater O is, the further aircraft need        to taxi and more (or different) land is required for the runway        arrangement. A distance of preferably a quarter to double the        width of one runway and more preferably substantially one runway        width (e.g. 40 m-75 m would be an appropriate compromise in one        example.

FIGS. 8(a)-(d) show ‘y-shaped’ runway arrangements that comprise threerunway sections and thus allow airport capacity to be improved furtheror offer alternative approach/departure paths for aircraft in order toprovide relief to nearby populations.

Specifically, FIG. 8(a) shows a further runway arrangement comprising asecond runway section 602-2 disposed at an angle to the first section602-1, and a third runway section 602-3 substantially in prolongation ofthe first runway section 602-1, thereby preferably forming a ‘y-shaped’runway arrangement. This further arrangement may be considered as FIG. 6superimposed onto that of FIG. 5(a), and indeed this may be the mannerin which the arrangement is constructed.

The arrangement shown in FIG. 8(a) allows for two differentapproach/departure paths (i.e. along runway sections 602-2 or 602-3),providing relief to the local population who would otherwise have beencontinually disturbed by one approach/departure path. For example,runway sections 602-2 and 602-3 are used on alternating days of theweek. If the curved approaches/departures illustrated in FIG. 7(a) arealso used, this advantage is magnified (e.g. by periodically varying thecurvature of the approach/departure).

The third runway section 602-3 comprises a sterile safety area 610 whichoverlaps with the sterile safety area between the first and secondrunway sections. Preferably, a single section of the runway arrangementpositioned at the intersection of the three runway sections is reservedas a sterile safety area 610 which aircraft can only use in exceptionalcircumstances. All three runway sections 602 are thereby linked by thecommon safety area 610.

When the arrangement is being used in Westerly operation (i.e. forWestward-bound aircraft landing on section 602-1), aircraft can useeither of runway sections 602-2 or 602-3 to take off. If two aircraftnot requiring a full length need to take off (for example, small orlighter aircraft), it would be possible for both these aircraft to takeoff simultaneously without interfering with landing aircraft on thefirst runway section 602-1. Each aircraft would taxi to a take-off point800-2, 800-3 on the respective runway section. These points arepositioned at a point towards the West of the runway sections, at adistance far enough along so that relative angle of the runway sectionsmeans that the aircraft are laterally separated. This distance ‘A’ isdependent on the angle θ and also local regulatory requirements forwing-tip clearance, in particular so as to avoid wing tip vortices fromone aircraft disturbing the other (for example, based on distancesgoverned by regulation).

A modification to the arrangement shown in FIG. 8(a) is shown in FIG.8(b) where the third runway section 602-3 is laterally offset from thesecond runway section 602-2, the direction of lateral offset beingopposite to the angle that the second runway section 602-2 is disposed.The first and third runway sections 602-1, 602-3 are laterally offset bya distance O′ (measured centreline to centreline between the ends of therunway sections). This arrangement may be considered as FIG. 6superimposed onto that of FIG. 5(b), and indeed this may be the mannerin which the arrangement is constructed.

The sterile safety areas 610, 610-3 (which may be combined as a singlesterile safety area, as shown in FIG. 5(d), thereby linking the threerunway sections) are not used for taxiing purposes; aircraft taxi eitherside of it, only passing through (and completely through) when executingan extended take-off or landing. If the runways are being used in the‘exceptional’ mode, departures and landings may need to be phased so asto allow aircraft to cross the runway. This operational restrictionmakes it less likely that an aircraft is present in the sterile safetyarea 610 when there is no such phasing (e.g. if a pilot believes he haspermission to use an extended runway when the air traffic controllershave not arranged for phased departures/landings).

The lateral distance the runway sections 602-3 and 602-1 may be offsetmay vary from a distance less than a runway width (i.e. so the runwaysection 602-3 overlaps with the other runway sections), for example froma quarter of the width of the runway sections 602-1, 602-2 or 602-3, upto a lateral distance twice the width of the runway section 602-1, 602-2or 602-3, preferably between a distance of around 50 m and 100 m andmore preferably between 60 m to 80 m. The greater the separation, thegreater safety is afforded, yet the total space required is increased,as well as the distance aircraft are required to taxi. If the separationis of a sufficient amount, two aircraft could take off simultaneouslyusing the full length of each runway section 602-2, 602-3 without theneed to taxi to points 800 as illustrated in FIG. 8(a).

In normal operation, taxiways T are used (indicated by solid lines)whereby aircraft utilise only the length of the runways not designatedas a safety area 610.

In exceptional circumstances (for example, where an aircraft isparticularly heavy or due to adverse weather conditions), the entirelength of a runway section may be used. The taxiways used in suchcircumstances are indicated by dashed lines. For example, in Westerlyoperations (aircraft moving towards the left of the Figure) an aircraftrequiring additional runway length to take-off may cross the lowerrunway section 602-1 outside of the sterile safety area 610 and utilisethe sterile safety area 610-3 of the third runway section 602-3 to takeoff. Similarly, if a greater distance is required to land, an aircraftmay utilise the sterile safety area 610 and taxi along line T aftercompletely traversing through the sterile safety area 610. Similartaxiways may be used when the arrangement is operating in the opposing(Easterly) direction.

FIG. 8(c) shows an alternative arrangement where the second (angled)runway section 602-2 is also offset from the first runway section 602-1,as shown in FIG. 7(b). This arrangement may suit locations where spaceis limited as it is particularly compact, whilst still affording theadvantage of the offset runways 602-2 and 602-3 making an overshoot ontothe first runway section 602-1 less likely.

FIG. 8(d) shows a modification to the runway arrangement shown in FIG.8(a) whereby an extension 810 to runway section 602-2 has been providedby using a triangle-like filet 820 between runway sections 602-2 and602-3 on which aircraft may taxi, take-off and/or land. This exampleallows the runway section 802-2 to be extended without greatlyincreasing the envelope of the airport.

FIGS. 9(a)-(c) show substantially the same ‘y-shaped’ runwayarrangements of FIGS. 8(a)-(d), but with a further runway section 652(which, in certain circumstances may be a pre-existing runway section,such as London Heathrow airport's Southern runway, along with runwaysection 602-1) offset by a distance D.

Specifically, FIG. 9(a) illustrates the runway arrangement of FIG. 8(a)with the further runway section 652. This arrangement may be consideredas a combination of arrangements illustrated by FIGS. 8(a) and 7(a). Asimilar arrangement corresponding to a combination of FIGS. 8(b) and7(a) is shown in FIG. 9(b), and a combination of FIGS. 8(c) and 7(b) isshown in FIG. 9(c). The same restrictions on the length (L), angle (θ)and starting point of the second runway section 602-2 apply to thesearrangements as to those described above with reference to FIG. 7.

FIG. 10 shows a set of two, in-line, angled runways (as illustrated inFIG. 6) parallel to one another. In such an arrangement two aircraft cantake off simultaneously and two aircraft can land simultaneously. Inorder for runway sections 652-1 and 602-2 to be used simultaneously,there must be no conflict of approach/departure paths on the two runwaysections. The centreline (C) of runway section 652-1 does not thereforeintersect with runway section 602-2. For this to be the case, theinequality D>L·sin(θ) must hold true, where D is the distance betweenthe centrelines of runway sections 602-1 and 652-1, L is the length ofrunway section 602-2, and θ is the angle at which runway section 602-2is disposed relative to runway section 602-1.

Furthermore, when no aircraft are departing (such as early in themorning) the distal runway sections (e.g. sections 602-1 and 652-1 whenlanding to the East) can be used for landings so as to lessen the noiseto a population close to the airport (as described above with referenceto FIG. 4(b)).

Table 3 below illustrates possible modes of simultaneous operation ofthe various runway arrangements described in FIGS. 5-10 and accordingmodes of controlling air traffic. It should be noted that these exampleoperational modes would be subject to local aircraft legislation andother physical operational requirements such as local topography andweather.

TABLE 3 Modes of Operation Figure & direction of operation Runwaysection Runway section Runway section Runway section Notes 5(a);Westerly 502-1 - 502-2 - NA NA Long landings can be made using section502-1 when Aircraft take off Aircraft land no aircraft are taking off.Similarly take offs can be made on section 502-2 when no aircraft arelanding 5(a); Easterly 502-1 - 502-2 - NA NA Long landings can be madeusing section 502-2 when Aircraft land Aircraft take off no aircraft aretaking off. Similarly take offs can be made on section 502-1 when noaircraft are landing 5(b)/(c)/(e); 502-1 - 502-2 - NA NA Long landingscan be made using section 502-1 when Westerly Aircraft take Aircraftland no aircraft are taking off. Similarly take offs can be off made onsection 502-2 when no aircraft are landing 5(b)/(c)/(e); 502-1 - 502-2 -NA NA Long landings can be made using section 502-2 when EasterlyAircraft land Aircraft take off no aircraft are taking off. Similarlytake offs can be made on section 502-1 when no aircraft are landing5(d); Westerly 502-1 - 502-2 - NA NA Long landings can be made usingsection 502-2 when Aircraft land Aircraft take off no aircraft aretaking off. Similarly take offs can be made on section 502-1 when noaircraft are landing 5(d); Easterly 502-1 - 502-2 - NA NA Long landingscan be made using section 502-1 when Aircraft take off Aircraft land noaircraft are taking off. Similarly take offs can be made on section502-2 when no aircraft are landing 6; Westerly 602-1 - 602-2 - NA NALong landings can be made using section 602-2 when Aircraft landAircraft take off no aircraft are taking off. Similarly take offs can bemade using section 602-1 when no aircraft are landing 6; Easterly602-1 - 602-2 - NA NA Long landings can be made using section 602-1 whenAircraft take off Aircraft land no aircraft are taking off. Similarlytake offs can be made using section 602-2 when no aircraft are landing7(a)/(b); 602-1 - 602-2 - 652 - Used in NA Long landings can be madeusing section 602-2 when Westerly Aircraft land Aircraft take off mixedmode - no aircraft are taking off. Similarly take offs can be aircrafttake made on section 602-1 when no aircraft are landing off and land tothe West in a phased manner 7(a)/(b); 602-1 - 602-2 - 652 - Used in NALong landings can be made using section 602-1 when Easterly Aircrafttake off Aircraft land mixed mode - no aircraft are taking off.Similarly take offs can be aircraft take made on section 602-2 when noaircraft are landing off and land to the East in a phased manner8(a)/(d); 602-1 - 602-2 - 602-3 - NA Long landings can be made usingeither section 602-2 Westerly Aircraft land Aircraft take off Aircrafttake off or 602-3 when no aircraft are taking off. Similarly take offscan be made using section 602-1 when no aircraft are landing. Sections602-2 and 602-3 may be used for simultaneous take offs by lighteraircraft using a shorter runway length. 8(a)/(d); 602-1 - 602-2 -602-3 - NA Either section 602-2 or 602-3 is used for landing, notEasterly Aircraft take off Aircraft land Aircraft land simultaneously.Long landings can be made using either section 602-1 when no aircraftare taking off. Similarly take offs can be made using section 602-2 or602-3 when no aircraft are landing. 8(b)/(c); 602-1 - 602-2 - 602-3 - NALong landings can be made using either section 602-2 Westerly Aircraftland Aircraft take off Aircraft take off or 602-3 when no aircraft aretaking off. Similarly take offs can be made using section 602-1 when noaircraft are landing. Sections 602-2 and 602-3 may be used forsimultaneous take offs using the entire runway length (if offset issufficient). 8(b)/(c); 602-1 - 602-2 - 602-3 - NA Either section 602-2or 602-3 is used for landing, not Easterly Aircraft take off Aircraftland Aircraft land simultaneously. Long landings can be made usingeither section 602-1 when no aircraft are taking off. Similarly takeoffs can be made using section 602-2 or 602-3 when no aircraft arelanding. 9(a); Westerly 602-1 - 602-2 - 602-3 - 652 - Used in Longlandings can be made using either section 602-2 Aircraft land Aircrafttake off Aircraft take off mixed mode - or 602-3 when no aircraft aretaking off. Similarly take aircraft take offs can be made using section602-1 when no aircraft off and land are landing. to the West in Sections602-2 and 602-3 may be used for a phased manner simultaneous take offsby lighter aircraft using a shorter runway length. 9(a); Easterly602-1 - 602-2 - 602-3 - 652 - Used in Either section 602-2 or 602-3 isused for landing, not Aircraft take off Aircraft land Aircraft landmixed mode - simultaneously. aircraft take Long landings can be madeusing either section 602-1 off and land when no aircraft are taking off.Similarly take offs can to the East in be made using section 602-2 or602-3 when no aircraft a phased manner are landing. 9(b)/(c); 602-1 -602-2 - 602-3 - 652 - Used in Either section 602-2 or 602-3 is used forlanding, not Westerly Aircraft land Aircraft take off Aircraft take offmixed mode - simultaneously. aircraft take Long landings can be madeusing either section 602-2 off and land or 602-3 when no aircraft aretaking off. Similarly take to the West in offs can be made using section602-1 when no aircraft a phased manner are landing. 9(b)/(c); 602-1 -602-2 - 602-3 - 652 - Used in Either section 602-2 or 602-3 is used forlanding, not Easterly Aircraft take off Aircraft land Aircraft landmixed mode - simultaneously. aircraft take Long landings can be madeusing either section 602-1 off and land when no aircraft are taking off.Similarly take offs can to the West in be made using section 602-2 or602-3 when no aircraft a phased manner are landing. 10; Westerly 602-1 -602-2 - 652-1 - 652-2 - Long landings can be made using sections 602-2Aircraft land Aircraft take off Aircraft land Aircraft take off and/or652-2 when no aircraft are taking off. Similarly take offs can be madeusing sections 602-1 and/or 652-1 when no aircraft are landing. 10;Easterly 602-1 602-2 652-1 - 652-2 - Long landings can be made usingsections 602-1 Aircraft take off Aircraft land Aircraft take offAircraft land and/or 652-1 when no aircraft are taking off. Similarlytake offs can be made using sections 602-2 and/or 652-2 when no aircraftare landing.

Further to the example modes of simultaneous operation detailed above,it would also be possible to have a mode of operation where just one ofthe two in-line runway sections is used (for example in mixed-mode, justfor take-offs, or just for landings). This may be useful for safetypurposes such as when one of the in-line runways is being repaired orcleared of snow; or during periods of infrequent aircraft movement.

Turning to methods of construction, the above-described runwayarrangements are constructed by providing the second and/or third runwayarrangements according to the arrangements described with reference toFIGS. 5-10. For example, in FIGS. 5(b)-(e), the second runway section502-2 is provided so that it is laterally offset from the first runwaysection 502-1. The safety area between the first and the second runwaysections is designated, for example as defined by a region where thefirst and second runway sections longitudinally overlap.

In other examples, such as in FIG. 6, the second runway section 602-2 isprovided at an angle to the first runway section 602-1, such that thesecond runway section 602-2 extends from the first runway section 602-1,via a sterile safety area 610, at an angle relative to the first runwaysection 602-1. By designating a sterile safety area 610 between thefirst and the second runway sections, the runway sections are in effectlinked by the sterile safety area 610. The steps of providing angled andlaterally offset runway sections may be combined in order to construct arunway arrangement as described with reference to FIG. 7(b).

In the example shown in FIG. 8(d), construction of the runwayarrangement is conducted by providing a triangle-like fillet 820 to theWest of the first runway section 602-1. The fillet 820, which issuitable for aircraft to taxi, take off from and land upon, covers anarea in which two further runway sections extending from the firstrunway section 602-1—the (angled) second runway section 602-2 and thethird runway section 602-3—are designated. An extension 810 to thesecond runway section 602-2 is designated such that the second runwaysection 602-2 extends across substantially the entirety of thehypotenuse of the triangle-like fillet 820.

Purely by way of example, Table 4 below illustrates the stages ofconstruction of the runway arrangements shown in FIGS. 5-10.

TABLE 4 Methods of Construction Fig- ure Stage 1 Stage 2 Stage 3 Stage 4Stage 5 Notes  5(a) Providing Expanding Eastwards Designating a NA NArunway by providing runway safety area 510 section section 502-2 inbetween runway 502-1 alignment with runway sections 502-1 and section502-1 502-2  5(b) Providing Expanding Eastwards Designating NA NA runwayby providing runway longitudinally section section 502-2, which isoverlapping safety 502-1 offset from runway areas 510-1 and section502-1 510-2  5(c) Providing Expanding Westwards Designating NA NA runwayby providing runway longitudinally section section 502-2, which isoverlapping safety 502-1 offset from runway areas 510-1 and section502-1 510-2  5(d) Providing Expanding Westwards Designating NA NA runwayby providing runway longitudinally section section 502-2, which isoverlapping sterile 502-1 offset from runway safety areas 510-1 section502-1 and 510-2  5(e) Providing Expanding Eastwards Designating safetyNA NA runway by providing runway area 510 between section section 502-2,which is runway sections 502-1 offset from runway 502-1 and 502-2section 502-1  6 Providing Expanding Westwards Designating a NA NArunway by providing runway safety area 610 section section 602-2 at anbetween runway 602-1 angle relative to runway sections 602-1 and section602-1 602-2  7(a) Providing Providing runway Expanding Designating asafety NA Runway sections runway section 652, parallel to Westwards byarea 610 between 602-1, 602-2 section and longitudinally providingrunway runway sections 602-1 and 652 are 602-1 aligned with runwaysection 602-2 at an and 602-2 arranged to section 602-1 angle relativeto satisfy runway section D > L · sin(θ) 602-1  7(b) Providing Providingrunway Expanding Designating a safety NA Runway sections runway section652, parallel to Westwards by area 610 between 602-1, 602-2 section andlongitudinally providing runway runway sections 602-1 and 652 are 602-1aligned with runway section 602-2 at an and 602-2 arranged to section602-1 angle relative to satisfy runway section D + O > L · sin(θ) 602-1 8(a) Providing Expanding Westwards Expanding Designating a safety NArunway by providing runway Westwards by area 610 between the sectionsection 602-3 providing runway runway sections 602-1, 602-1 section602-2 at an 602-2 and 602-3 angle relative to runway section 602-1  8(b)Providing Expanding Westwards Expanding Designating a safety NA runwayby providing runway Westwards by area 610 between section section 602-2at an providing runway runway sections 602-1 602-1 angle relative torunway section 602-3 and 602-2; and further section 602-1 designating asafety area 610-3 for runway section 602-3, such that safety areas 610-3and 610 longitudinally overlap  8(c) Providing Expanding WestwardsExpanding Designating a safety NA runway by providing runway Westwardsby area 610 between the section section 602-3 which is providing runwayrunway sections 602-1, 602-1 offset from runway section 602-2 602-2 and602-3 section 602-1 which is offset and angled relative to runwaysection 602-1  8(d) Providing Expanding Westwards Designating aDesignating a portion Designating a Runway section runway by providing atriangle- portion of the of the triangle-like fillet providing 602-2 issection like fillet 820 in triangle-like fillet 820 as runway sectionsafety area 610 extendable by 602-1 prolongation of runway 820 as runwayrunway section 602-2 between runway extension 810 section 602-1 section602-3, which is angled sections 602-1, across which is laterallyrelative to runway 602-2 and 602-3 substantially the aligned withsection 602-1 entire runway section hypotenuse of 602-1 thetriangle-like fillet 820  9(a) Providing Providing runway ExpandingExpanding Westwards Designating a Runway sections runway section 652,parallel to Westwards by by providing runway safety area 610 602-1,602-2 section and longitudinally providing runway section 602-2 at anbetween runway and 652 are 602-1 aligned with runway section 602-3 anglerelative to sections 602-1, arranged to section 602-1 runway section602-1 602-2 and 602-3 satisfy D > L · sin(θ)  9(b) Providing Providingrunway Expanding Expanding Westwards Designating safety Runway sectionsrunway section 652, parallel to Westwards by by providing runway area610 between 602-1, 602-2 section and longitudinally providing runwaysection 602-2 at an runway sections and 652 are 602-1 aligned withrunway section 602-3, angle relative to 602-1 and 602-2; arranged tosection 602-1 which is offset from runway section 602-1 and designatingsatisfy runway section safety area 610-3 D > L · sin(θ) 602-1 of runwaysection 602-3, such that safety areas 610-3 and 610 longitudinallyoverlap  9(c) Providing Providing runway Expanding Expanding WestwardsDesignating a Runway sections runway section 652, parallel to Westwardsby by providing runway safety area 610 602-1, 602-2 section andlongitudinally providing runway section 602-2 at an between the and 652are 602-1 aligned with runway section 602-3, angle relative to runwaysections arranged to section 602-1 which is offset from runway section602-1 602-1, 602-2 and satisfy runway section 602-3 D + O > L · sin(θ)602-1 10 Providing Providing runway Expanding Expanding WestwardsDesignating a The angles of runway section 652-1, parallel Westwards byby providing runway safety area 610 runway sections section to andlongitudinally providing runway section 652-2 at an between runway 602-2and 652-2 602-1 aligned with runway section 602-2 at an angle relativeto sections 602-1 and relative to section 602-1 angle relative to runwaysection 652-1, 602-2 and between sections 602-1 runway section parallelto and runway sections and 652-2 602-1 longitudinally aligned 652-1 and652-2 respectively are with runway section substantially 602-2 equal.Runway sections 602-1, 602-2 and 652-1 are arranged to satisfy D > L ·sin(θ).

RUNWAY THRESHOLDS

At any airport there is the possibility of a landing aircraft requiringto touch-down and immediately take off again (a ‘missed approach’),possibly due to a failure. In an extreme example, this may have to beperformed with the aircraft suffering from an engine failure which wouldlimit its ability to climb following take-off. In a typical runwayarrangement, the requirement following a missed approach is to be ableto climb to a sufficient height to avoid obstacles around the runway,such as fences or buildings. A 100 ft (30 m) separation above suchobstacles is a typical regulatory requirement. In practice, this mayresult in a 200 ft (60 m) height above the ground as the highest likelyobject to be cleared is a tail fin of a large aircraft (such as anAirbus A380), which is approximately 30 m high.

During simultaneous operation of an extended runway as described above,stricter requirements may be required for safe independent operation asa second aircraft may be taking off from the distal end of the runway atthe same time as the first aircraft is performing a land and take-offmanoeuvre on the proximal runway section. This may result in the faultylanding and taking-off aircraft interfering with the departing aircraftprior to turning so as to attempt a further landing (for example on adifferent runway section). In order to avoid such a scenario, thedimensions and layout of the extended runway arrangement can be tailoredso that the possibility of any interference is negligible.

FIG. 11a shows a plan view of a first aircraft 250-1 arriving and havingto perform a missed approach on a proximal section of runway 202-1whilst a second aircraft 250-2 is simultaneously taking off from adistal section of the extended runway 202-2. FIG. 11b a horizontalperspective of the same scenario illustrating the elevation of theaircraft performing the missed approach.

The distance relevant for safety considerations is ‘H’, the minimumheight an aircraft can be before being able to start turning away fromthe runway line. This minimum height allows the crew to reconfigure theaircraft and become sufficiently established in a stable climb. Itshould be appreciated that other distances are applicable in otherterritories and indeed other contexts (for example, particular aircraftor locations where different regulations apply). An aircraft performinga missed approach would typically turn by an angle of at least 20°,preferably at least 40°, so would quickly move away from any potentialinterference with departing aircraft.

The restriction on the minimum height that must be achieved prior toturning away from the runway arrangement 202 introduces a minimumdistance D between the point at which the first aircraft starts itsascent following a missed approach and the point a second aircraftstarts its ascent on the distal runway section:

$D > \frac{H}{\tan\;\theta_{1}}$

The distance D is effectively the separation between the last possiblelanding threshold on the landing runway section and start of thetake-off runway section. This distance may also comprise the (possiblynegligible) distance an aircraft travels along the runway beyond thelanding threshold before beginning its ascent (as shown by distance r₁in FIG. 11(b)).

For a typical turning minimum height H of 500 ft (152 m—approximately150 m) and varying θ₁, this gives the following approximate minimumdistances for D:

TABLE 5 Example minimum distances between take off points for a varietyof different angles of ascent following a missed approach θ₁ (degrees) D(meters) 2 4350 3 2900 4 2200 5 1750 6 1450 7 1250 8 1100

As illustrated in Table 5, the minimum value of D to provide a safemissed approach varies depending on the angle of ascent following amissed approach. In many of the cases, the minimum value of D would notbe set by the safety of such a go-around, rather by the required runwaydistance and intermediate safety area for a plane to land and come to asafe stop (as is discussed above with reference to FIGS. 2-10).

In practice, θ₁ is set by the poorest performing aircraft allowed toland (whilst maintaining independent operation) at a particular airportwhen suffering a single engine failure. The graph in FIG. 12 shows howthe distance D varies for various values of θ₁ when assuming a typicalvalue for H being 500 ft (152 m). This relationship allows an airportdesigner/operator to 1) select a value for D so as to ensure a certainclass of aircraft are safe to land whilst maintaining independentoperation; and/or 2) determine which classes of aircraft are safe toland whilst maintaining independent operation for a given D. Foraircraft that are able to climb between 2°-7° (when not fullyoperational), the minimum value for D varies between approximately 1,500m to 4,500 m. For aircraft that are able to climb between 2.5°-3.5°(when not fully operational), the minimum value for D varies betweenapproximately 2,500 m to 3,500 m.

Twin-engine aircraft such as older models of a Boeing 737-400 or anAirbus A320 are often the poorest performing aircraft in largecommercial airports (when suffering an engine failure); this class ofaircraft can ascend at 3 degrees or slightly greater with a singleengine failure. This provides a minimum value of D of approximately2,900 m.

If an aircraft not meeting a predefined minimum climb rate (for example,a very old aircraft) wishes to land, it may be necessary to suspendindependent operation of the runway arrangement until that aircraft hassafely landed.

There are a number of distances that affect the length D, these are asfollows:

-   -   L₁—the length of the landing runway 202-1    -   d₁—the distance from the start of the landing runway 202-1 to        when the first aircraft takes off following a failure    -   S—the length of the intermediate safety area 210

These distances are related by the following formula:D=S+L ₁ −d ₁

L₁ is typically determined by the distance required for an aircraft tocome to a safe stop following landing, as is described above. An exampledistance is 2-4 km, preferably 3 km, or 3,100 m.

The size of the intermediate safety areas 210 (S) is determined byregulatory and safety considerations so as to ensure a minimumseparation between aircraft. Such an area may also be used for aerialsor other ground equipment such as ILS aerials. A typical distance isaround 300 m-900 m, preferably 650 m.

d₁ is shown split into two distances r₁ and t₁ in FIG. 11b . d₁ definesthe ‘last touch-down point’ if an aircraft is not on an approach path totouch down by this point, it would not touch-down; rather the aircraftwould abort the landing, ascend again, turn and re-attempt the landing(in which case t₁≈d₁). The last touch-down point may be defined by thedistance required for an aircraft to safely come to a stop. The minimumdistance between this point and the start of the following runwaysection (D) therefore sets a restriction on the length of the safetyarea S and the length of the runway section L₁.

t₁ is the distance from the start of the landing runway 202-1 to thetouch-down point. This may be set in part by regulatory requirements(for example, the provision of a RESA as described above) and the skillof a pilot.

r₁ is the distance that an aircraft travels along the runway 202-1before taking off again. This may be determined by the capabilities ofthe aircraft in question, in many cases this distance may be negligible,with the aircraft briefly contacting the runway.

Substituting for D this gives a value for t₁ defined by variables setpredominantly by aircraft performance (i.e. θ₁, r₁, and L₁) andvariables set predominantly by regulatory requirements (i.e. H and S):

$t_{1} < {S + L_{1} - r_{1} - \frac{H}{\tan\;\theta_{1}}}$

It is clear from the equation above that an increase in H₁ or r₁necessitates a decrease in t₁; whereas an increase in of S, L₁ or θ₁relaxes the distance the ‘last touch-down point’ is to the start of thelanding runway section 202-1.

A lower limit of t₁ may be set by the desire to avoid pilots attemptingto land very close to the start of the landing runway section andtouching down on a section (such as a RESA) prior to the landing runwaysection not explicitly designated for landing. Gusts of wind at thefinal approach (or other external effects) may mean touch downs veryclose to the start of the landing runway section would be difficult torepeat with sufficient reliability. A lower limit of 300 m-500 m may beused.

In one example r₁ may be zero, or close to zero corresponding to theaircraft merely ‘grazing’ the landing runway.

For an example where H is 500 ft (152 m), S is 650 m, L₁ is 3,100 m, 0,is 3° and r₁ is zero this gives a value of t₁ of around <850 m. In sucha scenario, a landing zone is provided which is between around 300 m-800m from the start of the runway section.

In one example, the ‘last touch-down point’, t₁, is less than 100 m fromthe start of the landing runway. In another example, t₁ is between 100 mand 1,500 m from the start of the landing runway. In another example, t₁is between 100 m and 1,000 m from the start of the landing runway. Inanother example, t₁ is between 500 m and 800 m from the start of thelanding runway.

The above restrictions defining a ‘last touch-down point’ generallyapply to the scenario of an aircraft only becoming aware of a potentialproblem relatively close to the touch down point. In an alternativeexample, the distance D may be measured from the normal landingthreshold (i.e. substantially the start of the landing runway). Such aloosening of requirements may be allowed where an aircraft is aware of apotential problem, so aims to touch down closer than when the aircraftis fully operational.

In an alternative example, there is a point determined as the ‘missedapproach point’, typically a mile or further away from the start of therunway where an aircraft is deemed to be on a correct approach or not(e.g. at a particular height at a certain distance away from therunway). If an aircraft is not deemed to be on a correct approach path,it ascends to a suitable turning height (H) and re-attempts the landing.Where regulations allow, the distance D may be measured from the ‘missedapproach point’. In such an example, ‘H’ in the equation defining Dabove is in fact the difference between the height of the aircraft atthe missed approach point and the safe turning height.

If an aircraft suffers an engine failure prior to the ‘missed approachpoint’, independent operation may be suspended and/or the aircraft maybe directed to land on an alternative runway,

This type of restriction may be enforced by regulatory bodies as anengine failure occurring after the missed approach point would be veryrare. In such cases, one may assume that no engine failure would occur,so the climbing angle θ₁ may be greater, for example 10°. Such anassumption would loosen the requirement on the last touch-down point,extending it further down the landing runway section.

In a further alternative, any of the above restrictions on the point ofcalculation of D may be applied in combination. The three alternativesare summarised below in order of decreasing safety:

-   -   1. Last touch-down: A calculation based on an engine failure or        similar placing a restriction on the distance between the        furthest an aircraft could touch down (so as to safely land) but        still safely perform a missed approach in required.    -   2. Threshold: A calculation as per 1 above, but calculated from        the start of the landing runway section.    -   3. Missed approach point: A set of restrictions assuming either        an aircraft aborting an attempted landing and turning at a        missed approach point at a significant distance before the        landing runway, or assuming a fully operational aircracft.

Any of the above points may be called a ‘missed approach point’depending on the regulations in place. In any of the above cases, inorder for safe independent operation of an in-line runway arrangement,the distance between a missed approach point on a landing runway and thestart of a take-off runway is greater than a distance D. The distance Dis given by the formula D>H/tan θ₁.

Such a missed approach point may be physically marked on the runwayarrangement (for example by lights, a painted line) and/or may be markedvia software on an aircraft guidance system.

An angled or offset runway arrangement as described above with referenceto FIGS. 5(b) to 10 would increase the separation between two aircraftby a distance related to the extent of angling and/or offset; such anarrangement may therefore slacken the restriction on t₁ compared to asingle in-line extended runway as discussed above with reference toFIGS. 11 and 12.

RUNWAY LIGHTS

Aircraft pilots are guided into land, and to take off by numerousdifferent systems or methods; a common way to guide aircraft to landbeing runway markings and lights. Lights are typically used to indicatethe centre line and the edges of the runway so that the pilot does notstray outside the designated landing or take-off region.

When utilising an extended runway as described above with reference toFIGS. 2-10, there is the possibility that a landing pilot may confusethe lights on the distal take-off runway for the lights on the intendedlanding runway thereby landing on the incorrect runway (although othersystems such as ILS aerials and air traffic controllers would likelyreduce this possibility, if such systems are operational). Alternativelyor in addition, the lights on the distal take-off section may distractthe pilot from landing, or give the false impression of a single, longrunway.

A runway arrangement similar to that described above with reference toFIG. 2a is shown in FIG. 13 in a perspective view. In this embodiment,the runways are arranged substantially in-line on the same longitudinalaxis, with the runway arrangement comprising a proximal runway section202-1 and one distal runway section 202-2. The common longitudinal axiscan be indicated using a row of runway markings and/or lights 40, usedto assist a pilot in navigation of a runway during taxiing, take-off orlanding.

During conventional use, aircraft using the runway arrangement 202travel in substantially the same longitudinal direction. Landing occursat the proximal runway section 202-1 and take-off occurs at the distalrunway section 202-2.

The two runway sections are separated by a sterile Intermediate SafetyArea (ISA) 210-3. The presence of the ISA 210-3 lowers the risk ofcollision, should an aircraft landing on the proximal runway section202-1 overshoot the end of the runway section. The ISA 210-3 providesadditional space for such aircraft, and aircraft are not permitted toenter this area. Aircraft landing equipment such as ILS aerials may beplaced within the ISA 210-3 to aid aircraft in landing on the proximalrunway section 202-1 and taking off from the distal runway section202-2. Placement of such equipment within the intermediate section 210-3increase the quality of the signal as there would always be a directline of sight from the aerial to the aircraft requiring guidance (asdescribed above with reference to FIGS. 5 and 6).

The start of the proximal runway section 202-1 can be demarcated using arow of lights and/or runway markings and/or lights 30. These lightsand/or runway markings 30 assist the pilot in ascertaining the start ofthe runway, lights being particularly suitable in inclement weather orat night. The start of the ISA 210-3 can be similarly demarcated using arow of lights and/or runway markings 50. These lights and/or runwaymarkings 50 also display to the pilot the end of the runway located atthe proximal end 202-1 of the runway arrangement 202. The end of the ISA210-3 and the start of the proximal runway section 202-1 can besimilarly demarcated using another row of lights and/or runway markings55. The end of the distal runway section 202-2 can be displayed to apilot using a row of lights and/or runway markings 60.

It is important for the safety of the aircraft for any pilot attemptingto take off or land using the runway arrangement 202 to be aware of thewidth and precise location of the runway 202. The width is measuredperpendicularly to the longitudinal axis of the runway, demarcated usingthe lights 40. The runway arrangement 202 therefore further comprisesone or more lights 10 running parallel to the longitudinal axis of therunway arrangement 202, situated at the periphery of the runwayarrangement 202.

When approaching the runway arrangement 202 for a landing, the pilot mayconfuse the lights on the distal runway section 202-2 for the lights onthe intended proximal runway section 202-1, thereby landing on theincorrect runway. There is a further risk that the lights on the distaltake-off section may distract the pilot from landing, or give the falseimpression of a single, longer runway. It is therefore important for thelights 10, also referred to as ‘directional lights’ 10, to be visible toa pilot of an aircraft approaching to land on that particular section ofthe runway arrangement 202. Light directors 15 for directing the lightfrom the runway light source 10 are provided so as to inhibit lightemanating from the light source in a specified direction or range ofdirections.

The light directors 15 are advantageously arranged so that only thedirectional lights 10-1 from the proximal runway section 202-1 arevisible to a pilot approaching the runway arrangement 202 when landingan aircraft. Light from directional lights sources 10-2 situated on thedistal runway section 202-2 are substantially blocked by blocking means15 in the range of directions which may be seen by a pilot of anaircraft approaching landing on the proximal runway section 202-1. Insuch a way, the distal runway section 202-2 is designated as anon-landing runway section. The light directors 15 are arranged so thatthe directional lights sources 10-2 from the distal end 202-2 of therunway arrangement 202 are visible to a pilot taking off from the distalrunway section 202-2.

The light directors 15 may comprise means for selectively blocking light(such as blocking means). The blocking means may be adjustable so as tobe able to tailor the amount/extent of light that is blocked dependingon the location of the light source. An aircraft departing on the distalrunway section 202-2 would need to see the all the light sources 10-2along this runway section 202-2 at the start of this section. This meansthat the light sources 10-2 most proximal on the distal runway section202-2 can be blocked to a greater extent to those at the distal end ofthe runway section 202-2. Such a ‘tapering’ can be achieved by usingblocking means (as shown in FIGS. 11 to 13 below), using an opaquesection of material surrounding the light source 10-2, placing aphysical barrier between the light source 10-2 and the pilot, orreducing the brightness of the light source 10-2 such that they are notvisible from more than a certain distance.

In an alternative embodiment, the light directors 15 comprise a lens, orlens arrangement so that light is focussed so as to be directed only ina specified direction or range of directions.

As described above, conventionally the proximal runway section 202-1 isused for aircraft to land, and the distal runway section 202-2 is usedfor aircraft take off. However it can be advantageous in terms ofreducing disturbance to local communities if aircraft land at the distalend 202-2 of the runway arrangement 202 (referred to as a ‘longlanding’). In doing so, more of the flight path of the aircraft is overuninhabited runway, and the aircraft can approach the runway arrangement202 at a greater altitude than if it were aiming to land at the proximalend 202-1, leading to reduced disturbance for those living underneaththe flight path. The aircraft can be landed at the distal end 202-2 ofthe runway arrangement 202 if the distal end is not being used for atake-off, or if the aircraft is arriving at such a time when disturbanceis to be minimised.

In this scenario, the pilot should be able to see the directional lights10 surrounding the distal end 202-2 of the runway arrangement 202. Thesedirectional lights 10 are normally blocked in such a way that they arenot visible to pilots landing aircraft. In order to increase the safetyof the landing procedure on the distal end 202-2, one or more secondarylight sources 20 can be placed adjacent said directional lights 10, asshown in FIG. 14. The secondary light sources 20, when illuminated, canprovide information to the pilot regarding the location of the proximalend 202-2 of the runway arrangement 202, even when the blocking means 15block the light from the directional light sources 10 in that particulardirection. In an alternative embodiment, the blocking means 15 may bemovable so that the directional light sources 10 are visible by thelanding aircraft. In either embodiment, the lighting on the proximalrunway section 202-1 would be switched off so that the pilot isunambiguously directed to the distal runway section 202-2.

The description above describes the use of the runway arrangement 202 ina first orientation, whereby aircraft can land at the proximal end 202-1and take off at the distal end 202-2. As described above, the directionof the aircraft using each of the individual runways is substantiallysimilar and can be displayed as arrows or other markings on the runway90, 100. However the runway arrangement 202 can also be used in a secondorientation, whereby the direction of the aircraft using each of theindividual runways is longitudinally reversed. An aircraft can land atthe distal end 202-2 and travel towards the ISA 210-3 whilst an aircrafttakes off from the proximal end 202-1 away from the ISA 210-3.

In this second orientation, the same safety concerns apply, in that itis necessary for the pilot to be able to clearly see and identify thearea from which to take off or land the aircraft. The directional lightsources 10, blocking means 15 and secondary light sources 20 thereforecan be operable as a system to provide the pilot with this informationin either of the two orientations.

FIG. 14 shows a runway arrangement 202 wherein both directions ofoperation are possible whilst maintaining the light blocking feature asdescribed above with reference to FIG. 13. In the embodiment shown, thedirectional light sources 10-1 and 10-2 along the runway sections 202-1and 202-2 are mirror-images of one-another with mirrored light directors15. Secondary lighting 20 may be provided on both runway sections 202-1and 202-2 thereby to allow ‘long landings’ when the runway arrangementis used in either direction. However, long landings may only be used inone direction of operation (for example if the runway arrangement 202only has a significant population near one end), so secondary lighting20 may only be provided on one section. Alternatively, movable lightdirectors 15 may be provided as described above instead of (or inaddition to) secondary lighting 20.

FIG. 15 shows a perspective view of the sightline of pilots landing andtaking off from the runway arrangement 202, comparing the view from thelighting system 10-1, 10-2 at the proximal end 202-1 of the runwayarrangement 202 to that from the distal end 202-2 of the runwayarrangement 202. Light sources 10-2 on the distal runway section 202-2are inhibited by light directors 15 from shining in the direction of alanding aircraft approaching or on the proximal runway section 202-1.However, an aircraft on the distal runway section 202-2 is able to seethe light sources 10-2 all the way along the distal runway section 202-2so as to guide a take-off.

In one embodiment, the light sources 10-2 are not visible to the pilotof the landing aircraft until the start of the ISA 210-3 (indicated bythe lights and/or runway markings 50). This example would minimise thelikelihood of confusion as the pilot of the landing aircraft would neversee the lights on the distal runway section. However, such extremedirecting may inadvertently inhibit light from being directed in thedirection of an aircraft taking off. In a further embodiment the lightsources 10-2 become visible to the pilot of the landing aircraft oncethey have touched down on the proximal runway section 202-1.

This extent of blocking may be sufficient as by the time an aircraft hastouched down on the correct runway, it is unlikely that an overrun wouldoccur. In a further embodiment the light sources 10-2 become visible tothe pilot of the landing aircraft once they are at a distance from theproximal runway section 202-1 once they have planned their descent andtheir choice of runway has become clear. It therefore does not causeconfusion if the lights 10-2 are visible as well as the light sources10-1, as the pilot is already aware of the runway on which they are toland. Further embodiments are possible where the light sources 10-2become visible to the pilot of the landing aircraft at any distancebetween the distances mentioned above.

FIG. 16 shows a side view of the sightline of pilots landing and takingoff from the runway arrangement 202, comparing the view from thelighting sources 10-1 at the proximal end 202-1 of the runwayarrangement 202 to that from the distal end 202-2 of the runwayarrangement 202. As a result of the arrangement of the light blockingmeans 15, the directional light sources 10-1 at the proximal end 202-1are visible, whereas the directional light sources 10-2 at the distalend 202-2 are not. It is therefore made clearer to the pilot where thelanding is supposed to take place.

FIG. 17(a) shows light directors 15 (in the form of a means forselectively blocking light) beside a light source 10 so as to blocklight in a certain range of directions. The blocking means 15 in FIG.15(a) is shown as being able to rotate. This may be so that it can bemoved out of the way so that the light source 10 can perform thefunction of a secondary light 20, and/or for installation (oradjustment) purposes so as to allow adjustment of the angle of theblocking means 15. The rotation may be about an axis of the blockingmeans 15, or the blocking means 15 may be movable with respect to thelight source 10, for example, around a circle with the light source 10at the centre. Alternatively, the arrangement comprising the lightsource 10 and light blocker 15 may rotate.

FIG. 17(b) illustrates the relative placement of a directional lightsource 10 and a secondary light source 20.

FIG. 18(a) illustrates an embodiment of a directional light source 10,whereby the light source 10 is embedded in the surface of the runwayarrangement 202. The light blocker 15 comprises an opaque covering of aportion of the directional light source 10, blocking the emission oflight in a specified direction.

FIG. 18(b) illustrates a particular embodiment of a directional lightsource 10. As in FIG. 18(a), the light blocker 15 comprises an opaquecovering of a portion of the directional light source 10. However, inthis embodiment, the directional light source 10 is operable to rotateon an axis 25. The direction in which the light is blocked can thereforebe varied according to the direction from which the directional lightsource 10 is to be made visible. In this embodiment secondary lightsources 20 may not be required, as if an aircraft was to land on thedistal end 202-2 of the runway arrangement 202, or any other situationwhich required the use of the secondary light sources 20, thedirectional light sources 10 could be rotated about their shafts 25. Thelight could therefore be made visible to the pilot, whereas it would nothave been before.

A relatively simple manner in which the visibility of lights 10, 40 canbe tailored would be to make the light sources 10, 40 on the distalrunway section 202-2 dimmer (less bright) than those on the proximalrunway section 202-1. Aircraft taking off from the distal runway section202-2 only need to see runway light sources 10, 40 which are a maximumdistance of the length of the runway section 202-2 (i.e. being able tosee the furthest light sources 10, 40 when starting their take-off),however, aircraft approaching to land need to see landing light sources10, 40 from much further away. For this reason, dimming the lightsources 10, 40 on the distal runway section 202-2 would not adverselyaffect aircraft taking off. This approach may be used in conjunction tothe blocking means 15 described above.

The brightness (intensity) of the light sources 40, 10 may becontrollable (e.g. by air traffic controller) so as to switch which setof light sources is brighter when the mode of operation is changed (e.g.for ‘long landings’, or for when the direction of operation isreversed). In addition, the intensity of the light sources 40, 10 may beadjustable depending on the visibility. In low visibility conditions (<2mile visibility), it may not be possible for a landing aircraft toclearly see the light sources on the distal runway section 202-2, sofull intensity may be utilised to aid a taking-off aircraft.

A similar light blocking system as described above may be provided withrespect to the centreline light sources 40. Inhibiting landing pilotsfrom being able to see the centreline light sources on the distal runwaysection 202-2 would further reduce the potential for confusion as to onwhich runway section to land.

In an alternative embodiment, runway lighting using polarised light maybe utilised so that pilots are unambiguously directed to the correctlanding runway. In such an embodiment, the runway light sources 10-2,40-2 on the distal runway section 202-2 comprise means for emittinglight with a specific polarisation. A pilot approaching the runwayarrangement may utilise a means for blocking the light with the specificpolarisation so that it is less visible to him or her. The light fromthe runway light sources 10-1, 40-1 may either have no polarisation oran opposing polarisation so that less of this light is blocked by thepilot's means for blocking the light with the specific polarisation.

The means for blocking the light with the specific polarisation maycomprise, head-up display, helmet-mounted display, a screen between thepilot and the cockpit window, a polarising camera which the pilot viewsthrough a screen. Such devices may be used in addition to other‘artificial vision’ pilot aids such as augmented reality displays.

Visibility permitting, the means for blocking the light with thespecific polarisation may comprise glasses or goggles that the pilotwould wear during landing and/or a coating or covering applied to thecockpit window. Such devices may reduce the visibility of the landingapproach and thus may not be preferable in inclement weather.

The means for producing polarised light from the runway light sources10, 40 may comprise polarising filters, reflecting polarisers, and/orscattering polarisers. The specific polarisation may be horizontal,vertical, circular (clockwise or anticlockwise) or any combinationthereof.

In order for the runway arrangement 202 to be used in different modes(e.g. ‘long landings’ or for when the direction of operation isreversed), the polarisation of the runway light sources 10, 40 may beadjustable. In one embodiment, the polarising means is adapted to switchbetween a first polarisation indicating a landing runway section and asecond polarisation indicating a take-off runway section. In oneexample, switching polarisation comprises rotating a polarising filterby approximately 90°.

The use of polarised runway lighting to block the visibility of lightdirected towards a landing aircraft may be utilised instead of, or inaddition to, the physical blocking methods described above withreference to FIGS. 13 to 19.

ALTERNATIVES AND MODIFICATIONS

Although the above description refers to many examples where an airportrunway arrangement has two parallel runways, the invention extends tosituations where there is a single runway. This would be particularlyadvantageous in an urban environment where there is only space for asingle runway. Furthermore, the invention can also be applied toairports with more than one non-parallel runway. This would beparticularly advantageous in order to increase passenger capacity insituations where non-parallel runways are independently used dependingon wind conditions or where space constraints require runways to benon-parallel.

The above description includes numerous references to runway and airportconfiguration dimensions. These dimensions are merely examples and aperson skilled in the art would appreciate that these are dependent onfactors such as type of aircraft and the regulations covering theairport. Such modifications could be made by a person skilled in the artand therefore are within the scope of the invention.

In one example, the safety area 510 being sterile means that aircraft donot typically use this area for landings or taxiing during normaloperation. However, the sterile safety area 510 is used onlyinfrequently for take-offs, in particular when done in a phased manner,but would only use the area for landing or taxiing during adverse orexceptional circumstances.

Although many of the runway arrangements described above have beenexplicitly described as being combined together, any two runwayarrangements may be combined, for example, any two runway arrangementsas shown in FIG. 8 positioned side-by-side.

It should be appreciated that the orientation of the runway arrangementsdescribed above are only examples, alternate orientations (such as aNorth-South orientation, or the runway arrangement being angled in anopposing direction) would be possible depending on the location.Furthermore, extending a runway in a specific direction (for example, tothe West) could equally be performed in the opposing direction (forexample, to the East).

Other means for blocking light directed towards a landing aircraft maybe utilised, for example artificial vision video processing software mayremove or reduce the light detected originating from a runway sectionwhich is not to be used for landing.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

It will be understood that the present invention has been describedabove purely by way of example, and modifications of detail can be madewithin the scope of the invention.

Reference numerals appearing in the claims are by way of illustrationonly and shall have no limiting effect on the scope of the claims.

What is claimed is:
 1. A runway arrangement comprising: a first runwaysection; a second runway section; and a sterile safety area that isdesignated as not to be used for taxiing; wherein the first and secondrunway sections are linked by the sterile safety area, the sterilesafety area extending continuously from an end of the first runwaysection to an end of the second runway section such that the first andsecond runaway sections do not intersect with each other; and the secondrunway section extends away from the first runway section at an angle ofsubstantially 0.25-10 degrees to a longitudinal direction of the firstrunway section.
 2. The runway arrangement according to claim 1 whereinthe second runway section extends away from the first runway section atan angle of substantially 1-5 degrees to the longitudinal direction ofthe first runway section.
 3. The runway arrangement according to claim 1wherein the second runway section is laterally offset from the firstrunway section.
 4. The runway arrangement according to claim 3, whereinthe lateral offset is in an opposite direction to the direction thesecond runway section is angled and/or wherein the second runway sectionis laterally offset from the first runway section by at least one of:between a quarter and double the width of the first runway section, andbetween 50 m and 100 m.
 5. The runway arrangement according to claim 1further comprising a laterally offset third runway section substantiallyparallel to, and substantially longitudinally aligned with, said firstrunway section.
 6. The runway arrangement according to claim 5, whereinthe second runway section is angled from the sterile safety area in adirection towards the laterally offset third runway section.
 7. Therunway arrangement according to claim 5 wherein the laterally offsetthird runway section is laterally offset from said first runway sectionso that the centerline of the laterally offset third runway section doesnot intersect with the second runway section, preferably wherein therunway arrangement satisfies the inequality D>L·sin(θ) or D+O>L·sin(θ),where D is the separation between the first runway section and thelaterally offset third runway section, L is the length of the secondrunway section, θ is the angle of the second runway section to the firstrunway section, and O is the distance between the centrelines of thefirst runway section and the second runway section at the ends of thefirst runway section and the second runway section.
 8. A runwayarrangement comprising: a first runway section; a second runway section;and a sterile safety area that is designated as not to be used fortaxiing, the sterile safety area extending continuously from an end ofthe first runway section to an end of the second runway section suchthat the first and second runaway sections do not intersect with eachother; wherein the second runway section is laterally offset from thefirst runway section, the second runway section extending away from thefirst runway section at an angle of substantially 0.25-10 degrees to alongitudinal direction of the first runway section; and wherein thesterile safety area comprises a first portion in prolongation of thefirst runway section and a second portion in prolongation of the secondrunway section, the first portion longitudinally overlapping with thesecond portion in an overlapping section.
 9. The runway arrangementaccording to claim 8 wherein the first runway section is a landingsection directed towards the overlapping section and the second runwaysection is a take off section directed away from the overlappingsection.
 10. The runway arrangement according to claim 8 wherein theoverlapping section is between 300 m and 900 m in length.
 11. The runwayarrangement according to claim 8 wherein the second runway section islaterally offset from the first runway section by at least one of:between a quarter and double the width of the first runway section, andbetween 50 m and 100 m.
 12. The runway arrangement according to claim 8further comprising a taxiway outside of the sterile safety area so as toallow access across the first runway section to a proximal end of thesecond runway section.
 13. The runway arrangement according to claim 8,wherein the first runway section extends from the first portion in afirst direction and the second runway section extends from the secondportion in a second direction; wherein the first direction and thesecond direction are different directions.
 14. The runway arrangementaccording to claim 8, wherein the first portion and the second portionof the sterile safety area overlap along the entirety of the length ofthe first portion and the second portion.
 15. The runway arrangementaccording to claim 8, wherein the first portion and the second portionare contiguous.
 16. A method of constructing a runway arrangement themethod comprising: providing a first runway section; providing a secondrunway section, the second runway section extending away from the firstrunway section at an angle of substantially 0.25-10 degrees to alongitudinal direction of the first runway section; providing a sterilesafety area linking the first runway section and the second runwaysection, the sterile safety area extending continuously from an end ofthe first runway section to an end of the second runway section suchthat the first and second runaway sections do not intersect with eachother; and designating the sterile safety area as not to be used fortaxiing.
 17. A method of constructing a runway arrangement, the methodcomprising: providing a first runway section; providing a second runwaysection; providing a sterile safety area; and designating the sterilesafety area as not to be used for taxiing, the sterile safety areaextending continuously from an end of the first runway section to an endof the second runway section such that the first and second runawaysections do not intersect with each other; wherein the second runwaysection is laterally offset from the first runway section, the secondrunway section extending away from the first runway section at an angleof substantially 0.25-10 degrees to a longitudinal direction of thefirst runway section; and wherein the sterile safety area comprises afirst portion in prolongation of the first runway section and a secondportion in prolongation of the second runway section, the first portionlongitudinally overlapping with the second portion.